Alternate doping of p-type and n-type impurities for AlGaInPselfaligned stepped substrate (S3) lasers

The authors fabricated lateral pn junctions in AlGaInP by alternate doping on a stepped substrate composed of (100) and (411)A faces with Zn and Se. It was found that the alternately-doped area on the (100) face becomes a uniform n-type conduction region; this is attributed to carrier depletion in lightly Zn-doped regions. The alternately-doped area on the (411)A face becomes a uniform p-type conduction region due to strong Zn diffusion over the lightly Se-doped regions. Using alternate doping, the authors fabricated a selfaligned stepped substrate (S³) laser. The low resistivity and high-power operation (50°C 35 mW) of this laser are comparable to those of lasers fabricated using simultaneous impurity doping     

Growth of GaInP/GaAsP short period superlattices by flow modulation organometallic vapor phase epitaxy

One disadvantage of the GalnP/GaAs system is the difficulty often encountered in synthesizing the quaternary material GalnAsP, required to span the intermediate bandgap range (1.42–1.91 eV). Recent studies report on an extensive miscibility gap in this alloy. In this study, we investigate an alternative approach to the growth of material within this bandgap range. We have grown by flow-modulation organometallic vapor phase epitaxy, GalnP/GaAsP superlattices with periods ranging from 80 to 21Å. These are the first reported short-period superlattices in this material system. Effects of superlattice (SL) period, growth temperature, and phosphorous composition in the wells were studied by photoluminescence, high resolution x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The effect of growth temperature on the structural quality of the SLs is correlated to ordering effects in the GalnP layers. Variations in the P composition and the SL period result in a shift in the room temperature bandgap emission from 1.51 to 1.74 eV. Strain-compensated structures have been realized by growing the SL barriers in compression.     

InSb分子束外延原位掺杂技术研究

对InSb分子束外延薄膜的本征掺杂、N型掺杂以及P型掺杂进行了研究,其中分别以Be作P 型以及以Si、Te作N 型的掺杂剂。实验采用半绝缘的GaAs衬底作为InSb分子束外延用衬底,通过采用低温生长缓冲层技术降低大失配应力,获得高质量InSb外延膜。实验样品采用霍尔测试以及SIMS测试掺杂浓度和迁移率分析掺杂规律、掺杂元素偏聚和激活规律的影响因素。     

Cu-Phosphorus Eutectic Solid Solution for Growth of Multilayer Graphene with Widely Tunable Doping

A one-step chemical vapor deposition (CVD) is proposed to grow multilayer graphene (MLG) with tunable doping types using a copper–phosphorus eutectic system as a catalyst. At the growth temperature, the phosphorus-dissolved copper forms a liquid phase, which promotes the formation of phosphorus-doped MLG. With this method, the thickness and doping level of graphene are simultaneously controlled at the synthesis stage. Moreover, the proposed CVD method enables patterned growth of MLG at the microscale. The resultant phosphorus-doped graphene demonstrates a tunable doping state from large n-type doping to p-type doping because of the high affinity of phosphorus to water molecules. Finally, stable n-type doping of MLG by passivating it with a parylene thin film is demonstrated.     

Structural and optical characterization of InP/GalnP islands grown by solid-source MBE

We report on the growth of InP/GalnP islands on GaAs substrates by solidsource molecular beam epitaxy. It is shown by reflection high energy electron diffraction and atomic force microscopy that a rapid change from a twodimensional to a three-dimensional growth mode occurs at about nominally 1.5 monolayers (MLs) InP. Transmission electron microscopy measurements demonstrate the coherent incorporation of InP islands in an GalnP matrix for nominally 2.5 MLs InP. The energy of the InP photoluminescence (PL) shifts to lower energies (100 meV) when the growth interruption time between the island and cap layer growth is increased from 1 to 300 s in case of nominally 3 MLs InP. Simultaneously, an increase of the PL linewidth is observed from 30 to 60 meV. Room temperature photoreflectance measurements on samples with various InP thickness have been performed. Compared to PL measurements, an additional feature in the photoreflectance spectra is observed for samples with more than 7 MLs InP, which is attributed to a transition between excited electron and hole states of the islands.     

Determination of the Band Offset of GalnP- GaAs and AllnP- GaAs Quantum Wells by Optical Spectroscopy

We report the determination of band offset ratios, using photoluminescence excitation measurements, for GaInP/GaAs and AlInP/GaAs quantum wells grown by gas-source molecular beam epitaxy. To reduce the uncertainty related to the intermixing layer at heterointerfaces, the residual group-V source evacuation time was optimized for abrupt GalnP/GaAs (AlInP/GaAs) interfaces. Based upon thickness and composition values determined by double-crystal x-ray diffraction simulation and cross-sectional transmission electron microscopy, the transition energies of GalnP/GaAs and AlInP/GaAs quantum wells were calculated using a three-band Kane model with varying band-offset ratios. The best fit of measured data to calculated transition energies suggests that the valence-band offset ratio (γ band discontinuity) was 0.63 ± 0.05 for GalnP/GaAs and 0.54 ± 0.05 for AlInP/GaAs heterostructures. This result showed good agreement with photoluminescence data, indicating that the value is independent of temperature.     

Monomolecular layer epitaxy of GaAs for ideal static induction transistor

An ideal static induction transistor (ISIT) structure was fabricated using molecular layer epitaxy (MLE). The doping method of MLE enabled us to achieve a sufficiently high level of doping for ISIT fabrication. In the fabrication process a low growth temperature was very important for the device structure, which requires very sharp dopant profiles. For the ISIT, two MLE processes, namely source–drain growth and gate regrowth, were required. The electrical characteristics of the source–drain were changed after heat treatment at a temperature higher than 480°C. The effect of the redistribution of dopants of the source–drain structure (n⁺⁺–i–p⁺⁺–i–n⁺) during gate regrowth was clearly shown by SIMS (secondary ion mass spectroscopy) measurements for various temperatures of heat treatment. As a result the doped Se diffused from the n⁺⁺ source region to the other layers and the doped Zn diffused from the p⁺⁺ layer to the i-layers. The source was a heavily Se-doped layer at the doping level of (2–3)×10¹⁹ cm⁻³ containing a larger amount of interstitial Se atoms in the lattice. The redistribution of Se from the heavily doped region was detectable even after heat treatment at 480°C for 30 min. For the p⁺⁺ layer the profile of the C-doped layer was stable even after heat treatment at 620°C for 30 min, but the profile of Zn changed markedly after heat treatment at 480°C for 30 min. In addition, the carbon-doped p⁺⁺ layer acted as a gettering layer for diffused interstitial Se from the source region. The driving force of the redistribution of dopants results in the electric field in the device structures. © 1997 John Wiley & Sons, Ltd.     

Some characteristics of highly N-doped VPE grown GaAs epilayers

The doping behaviour of S and Se in the VPE growth of GaAs at 760 and 660°C is studied by carrier concentra-tion, mobility, photo and cathodoluminescence measure-ments. The carrier concentration increases linearly with the partial pressure of S or H₂Se up to a solubi-lity limit, the highest value of which is obtained with Se at about 10¹⁹cm^-3. The mobility for Se-doped layers is higher than for S-doped ones when n > 4.10¹⁷cm^-3, and a mobility decrease is observed for both at dopings exceeding the solubility limit. Postgrowth annealing at the growth temperature of highly doped samples decreases their carrier concentration to values corresponding to the bulk solubility limit. The decrease of the room temperature luminescence intensity at high doping levels in tentatively interpreted as due to precipitate for-mation. Finally, the linear dependence on the dopant partial pressure of the impurity incorporation as well as the observed annealing behaviour are interpreted by an incorporation mechanism controlled by the surface states.     

优化主氢流量及C/Si比提高76.2mm4H-SiC同质外延浓度均匀性

源在外延片直径方向上的耗尽导致了外延片上局部各点的生长速率及掺杂浓度是个随位置变化的量,因此造成了外延片厚度及浓度的不均匀性.通过引入基座气浮旋转可以有效降低这种不均匀性,在典型工艺条件下,采用基座旋转,76.2 mm 4H-SiC外延片厚度不均匀性、p型掺杂浓度不均匀性和n型掺杂不均匀性分别为0.21%、1.13%和...     

1.3-μm InAsP modulation-doped MQW lasers

The effect of both n-type and p-type modulation doping on multiple-quantum-well (MQW) laser performances was studied using gas-source molecular beam epitaxy (MBE) with the object of the further improvement of long-wavelength strained MQW lasers. The obtained threshold current density was as low as 250 A/cm² for 1200-μm-long devices in n-type modulation-doped MQW (MD-MQW) lasers. A very low CW threshold current of 0.9 mA was obtained in 1.3-μm InAsP n-type MD-MQW lasers at room temperature, which is the lowest ever reported for long-wavelength lasers using n-type modulation doping, and the lowest value for lasers grown by all kinds of MBE in the long-wavelength region. Both a reduction of the threshold current and the carrier lifetime in n-type MD MQW lasers caused the reduction of the turn-on delay time by about 30%. The 1.3-μm InAsP strained MQW lasers using n-type modulation doping with very low power consumption and small turn-on delay time are very attractive for laser array applications in high-density parallel optical interconnection systems. On the other hand, the differential gain was confirmed to increase by a factor of 1.34 for p-type MD MQW lasers (N_A=5×10¹⁸ cm ^-3) as compared with undoped MQW lasers, and the turn-on delay time was reduced by about 20% as compared with undoped MQW lasers. These results indicate that p-type modulation doping is suitable for high-speed lasers     

Doping of gallium nitride using disilane

The silicon doping of n-type GaN using disilane has been demonstrated for films grown on sapphire substrates by low pressure organometallic vapor phase epitaxy. The binding energy of an exciton bound to a neutral Si donor has been determined from low temperature (6K) photoluminescence spectra to be 8.6 meV. Nearly complete activation of the Si impurity atom in the GaN lattice has been observed.     

The interface of metalorganic chemical vapor deposition-CdTe/HgCdTe

The metalorganic chemical vapor deposition (MOCVD) growth of CdTe on bulk n-type HgCdTe is reported and the resulting interfaces are investigated. Metalinsulator-semiconductor test structures are processed and their electrical properties are measured by capacitance-voltage and current-voltage characteristics. The MOCVD CdTe which was developed in this study, exhibits excellent dielectric, insulating, and mechano-chemical properties as well as interface properties, as exhibited by MIS devices where the MOCVD CdTe is the single insulator. Interfaces characterized by slight accumulation and a small or negligible hysteresis, are demonstrated. The passivation properties of CdTe/ HgCdTe heterostructures are predicted by modeling the band diagram of abrupt and graded P-CdTe/n-HgCdTe heterostructures. The analysis includes the effect of valence band offset and interface charges on the surface potentials at abrupt hetero-interface, for typical doping levels of the n-type layers and the MOCVD grown CdTe. In the case of graded heterojunctions, the effect of grading on the band diagram for various doping levels is studied, while taking into consideration a generally accepted valence band offset. The MOCVD CdTe with additional pre and post treatments and anneal form the basis of a photodiode with a new design. The new device architecture is based on a combination of a p-on-n homojunction in a single layer of n-type HgCdTe and the CdTe/HgCdTe heterostructure for passivation.     

Metalorganic chemical vapor deposition of HgCdTe for photodiode applications

Metalorganic chemical vapor depositon (MOCVD) in situ growth of p-on-n junctions for long wavelength infrared (LWIR) and medium wavelength infrared (MWIR) photodiodes is reported. The interdiffused multilayer process was used for the growth of the HgCdTe junctions on CdTe and CdZnTe substrates. The n-type region was grown undoped while the p-type layer was arsenic doped using tertiarybutylarsine. Following a low temperature anneal in Hg vapor, carrier densities of (0.2-2) x 10¹⁵ cm³ and mobilities of (0.7-1.2) x 10⁵ cm²/V-s were obtained for n-type LWIR (x ~ 0.22) layers at 80K. Carrier lifetimes of these layers at 80 K are ~l-2 μs. For the p-type region arsenic doping was controlled in the range of (1-20) x 10¹⁶ cm^-3. Arsenic doping levels in the junctions were determined by calibrated secondary ion mass spectroscopy depth profile measurements. Composition and doping of the p-on-n heterojunctions could be independently controlled so that the electrical junction could be located deeper than the change in the composition. The graded composition region between the narrow and wide (x = 0.28-0.30) bandgap regions are 1–2 μm depending on the growth temperature. Backside-illuminated variable-area circular mesa photodiode arrays were fabricated on the grown junctions as well as on ion implanted n-on-p MWIR junctions. The spectral responses are classical in shape. Quantum efficiencies at 80K are 42–77% for devices without anti-reflection coating and with cutoff wavelengths of 4.8–11.0 μm. Quantum efficiencies are independent of reverse bias voltage and do not decrease strongly at lower temperatures indicating that valence band barrier effects are not present. 80K R_oA of 15.9 Ω-cm² was obtained for an array with 11.0 μm cutoff. Detailed measurements of the characteristics of the MOCVD in situ grown and implanted photodiodes are reported.     

Low temperature growth and planar doping of ZnSe in a plasma-stimulated LP-MOVPE system

In a low-pressure metalorganic vapor phase epitaxy process, we used dc-plasma activated nitrogen to dope ZnSe, grown with ditertiarybutylselenide and dimethylzinc-triethylamine. The nitrogen concentration of up to 2 × 10¹⁸ cm⁻³ in the doped layers can be adjusted by the growth temperature, the dc-plasma power, and the N₂ dopant flow. Due to the high n-type background carrier concentration of the order of 10¹⁷ cm⁻³ in undoped samples, the doped layers show n-type conductivity or were semi-insulating because of an additional compensation by hydrogen incorporated with a concentration of the order of 10¹⁸ cm⁻³. A planar doping scheme was applied to reduce this hydrogen incorporation by one order of magnitude, although H₂ was used as carrier gas.     

Role of cadmium in enhancing optical properties and chlorine doping of photo-assisted OMVPE-grown znse

The influence of cadmium doping in enhancing: (i) near-band edge (NBE) to deep-level emissions (DLE) photoluminescence intensity ratio, and (ii) chlorine incorporation in HCl doped ZnSe films, has been studied. The epitaxial ZnSe was grown using low-temperature photo-assisted organometallic vapor phase epitaxy (OMVPE) using DMSe, DMZn, and DMCd alkyl sources. More intense near band-edge emission is observed when the growth temperature is reduced from 400 to 360°C. The deep-level emissions show a threshold-like dependence on UV light intensity for a given temperature. Cadmium doping is found to improve the NBE/DLE photoluminescence intensity ratio, and this improvement is more pronounced at higher growth temperature. Properties of n-type ZnSe films codoped with cadmium and chlorine, using HCl and DMCd as dopant sources have also been investigated. Samples co-doped with Cd showed higher electron concentrations and this effect was more pronounced at lower UV intensities. By the use of Cd co-doping, we have achieved the highest electron concentrations (2.4 x 10¹⁸ cm^-3) yet reported for HCl doping of OMVPE-grown ZnSe.     

InAs-based p-n homojunction diodes: Doping effects and impact of doping on device parameters

InAs heterojunction bipolar transistors (HBTs) are promising candidates for low power and high frequency (THz) device applications due to their small bandgap, high electron mobility, and high saturation drift velocity. However, doping limits such as the trade-off between desired low intentional n-type concentrations and unintentional doping, and the realization of high p-type concentrations, must still be considered in device design and synthesis. In order to observe the impact of intentional and unintentional n-type doping on diode electrical properties, InAs-based homojunction diodes have been grown on InAs substrates by solid-source molecular beam epitaxy (SSMBE) and were subsequently fabricated and characterized.     

Fundamental materials studies of undoped, In-doped, and As-doped Hg1−xCdxTe

Variable magnetic-field Hall and transient photoconductance-lifetime measurements were performed on a series of undoped, In-doped, and As-doped HgCdTe samples grown by molecular beam epitaxy (MBE). Use of quantitative mobility-spectrum analysis (QMSA) combined with multiple carrier-fitting (MCF) techniques indicates that the majority of samples contain an interfacial n-type layer that significantly influences the interpretation of the electrical measurements. This n-type layer completely masks the high-quality electrical properties of undoped or low n-type In-doped HgCdTe, as well as complicating the interpretation of activation in As-doped p-type HgCdTe. Introduction of an intentional n-type background, typically created through doping with In to “recover” high mobility, is actually shown to increase the “bulk” layer conductivity to a level comparable to the interface layer conductivity. Photoconductance-lifetime measurements suggest that In-doping may introduce Shockley-Read-Hall (SRH) recombination centers. Variable-field Hall analysis is shown to be essential for characterizing p-type material. Photoconductance-lifetime measurements suggest that trapping states may be introduced during the incorporation and activation of As. Two distinctly different types of temperature dependencies were observed for the lifetimes of As-doped samples.     

Growth rate reduction in self-limiting growth of doped GaAs by molecular layer epitaxy

Self-limiting growth of GaAs with doping by molecular layer epitaxy (MLE) has been studied using the intermittent supply of TEG, AsH₃, and a dopant precursor, Te(C₂H₅)₂ (diethyl-tellurium: DETe) for n-type growth on GaAs (0 0 1). The self-limiting monolayer growth is applicable at 265°C, however, the growth rate per cycle of doping decreased and saturated at about 0.4 monolayer with increasing doping concentration. To clarify the mechanism of growth with doping and to solve the problem of the growth rate reduction, a doping cycle followed by several cycles of undoped growth was performed. The growth rate reduction in the TEG–AsH₃ system is due to the electrical characteristics of the growing surface, namely, the exchange reaction of TEG is reduced with increasing doping concentration.     

InAs/GaAs量子点中间带太阳电池的理论研究与优化

从荧光粉散射机理分析了LED器件色角向分布不均匀的形成原因,提出了一种利用逐点步进光学设计方法,实现了不同入射角度内蓝光光程相等的远荧光粉层结构。应用该方法设计了使用不同折射率载体的LED远荧光粉层光学结构。模拟结果显示,应用所设计的光学形状的远荧光粉层结构,相比传统平面荧光粉层结构,75°方向光斑边缘与中心法线方向色差du′v′从0.05降低到0.01左右,色温偏移降低了43%~98%不等,有效改善了白光LED远程荧光粉封装结构的色度均匀性。该设计不需要增加或改变封装工艺手段,工业生产实现简单,额外成本很少,具有较强的实际应用价值。 更多还原     

Investigation of HgCdTe p-n device structures grown by liquid-phase epitaxy

The microstructure of p-n device structures grown by liquid-phase epitaxy (LPE) on CdZnTe substrates has been evaluated using transmission electron microscopy (TEM). The devices consisted of thick (∼21-μm) n-type layers and thin (∼1.6-μm) p-type layers, with final CdTe (∼0.5 μm) passivation layers. Initial observations revealed small defects, both within the n-type layer (doped with 8×10¹⁴/cm³ of In) and also within the p-type layer but at a much reduced level. These defects were not visible, however, in cross-sectional samples prepared by ion milling with the sample held at liquid nitrogen temperature. Only isolated growth defects were observed in samples having low indium doping levels (2×10¹⁴/cm³). The CdTe passivation layers were generally columnar and polycrystalline, and interfaces with the p-type HgCdTe layers were uneven. No obvious structural changes were apparent in the region of the CdTe/HgCdTe interfaces as a result of annealing at 250°C.