Lattice constant,bandgap, thickness,and surface morphology of InGaAsP-InP layers grown by step-cooling,equilibrium-cooling,supercooling and two-phase-solution growth techniques

Constant composition InGaAsP epitaxial layers can be grown on (100) InP substrates at a constant temperature using the diffusion-limited step-cooling growth technique, and in general, compositionally graded layers result when the diffusion-limited equilibrium-cooling, supercooling, and two-phase-solution growth techniques are used. The lattice constant and energy gap of the epitaxial layers grown using the step-cooling technique are nearly independent of small variations of X _p ^l and the amount of step cooling, but are dependent on growth temperature. The dependence of lattice constant and energy gap of the epitaxial layers on X _Ga ^l and X _As ^l has been determined for the step-cooling and supercool ing techniques.     

Metallurgical comparison of Au and Au:An:Au contacts on InGaAs,InGaAsP layers

A metallurgical study of the interaction between Au and InGaAs, InGaAsP and the role of the dopant (Zn) in this interaction has been conducted using TEM, AES and x-ray diffraction. Au alloyed with InGaAs reveals a single layer of large and rounded grains (2000Å in diameter). However, alloyed Au:Zn:Au on InGaAs and InGaAsP forms a continuous chain of spikes penetrating into the semiconductor. This spike morphology produces enhanced local current densities across the contact, and may affect laser reliability. A study of the kinetics of the interaction between the Au layer and InGaAs, reveals two major stages. The first stage is dominated by In out-diffusion and Au-rich Au₄In compound formation. In the second stage of the interaction, the Au-rich Au₄In compound starts to dissolve and Au₇In₃, Au₂Ga and Au₃P₂ (in the case of the quaternary layer) are formed. At certain temperatures, the presence of Zn in the Au layer shortens the time required for completing the first stage and beginning the second stage of the interaction. A thermal stability study reveals metallurgical instability at low tempeature (200° C) which does not reach completion even after alloying at 400° C for 4 hr.     

Optoelectronic properties of transition metal and rare earth doped epitaxial layers on InP for magneto-optics

Rare earth-and transition metal-doped thin films of InP, In_0.53Ga_0.47As, and In_0.71Ga_0.29As_0.58P_0.42 were grown by liquid phase epitaxy and evaluated for use in integrated electro-optical and magneto-optical applications, such as waveguides and Faraday rotators. The films were lattice matched to (100) InP substrates, and the transition metal (Mn) and rare earth (Gd, Eu, and Er) doping concentra-tions were between 2.6 × 10¹⁸ and 1.5 × 10²⁰ cm^-3. The chemical profiles were generally found to be homogeneous by SIMS, although in more highly doped films the rare earths were observed to segregate toward the interfaces. The undoped films were n-type, and the net carrier concentrations in the rare earth-doped (Gd, Eu, Er) films were decreased by an order of magnitude. The Mn-doped films were p-type. Optically, the rare earth dopants were observed to raise the refractive index of the layers at 632.8 nm, and subsequent waveguiding in doped InP layers was observed at 1.3 μm. Although the Faraday rotations of our materials were much less than that of well known oxides, such as yttrium iron garnet, they were sufficient for device applications, and our materials can be much more easily integrated with InP OEIC devices. For example, a 1 cm waveguide would provide the large rotation (45°) required in isolator applica-tions.     

Impact of growth rate on the quality of ZNS-MQW InGaAsP/InP laser structures grown by LP-MOVPE

We investigated the influence of the growth rate on the quality of zero-net-strained InGaAsP/InGaAsP/InP multiquantum well structures for 1.55 μm emission grown by low pressure metalorganic vapor phase epitaxy. The samples consisted of fixed compressive strained wells (ɛ=+1%) and tensile strained barriers (ɛ=−0.5%) grown with different quaternary bandgap wavelengths (λ_B=1.1–1.4 μm). Using higher growth rates, we obtained for the first time high quality zero net strained multi quantum well structures, regardless having constant group V composition in the well and barriers. The samples were analyzed by x-ray diffraction, photoluminescence and atomic force microscopy techniques. The amplitude of surface modulation roughness along [011] direction decreased from 20 nm to 0.53 nm with increasing growth rate and/or quaternary compositions grown outside the miscibility gap. A new deep PL broad emission band strongly correlated with the onset of wavy layer growth is also reported. Broad area and ridge waveguide lasers with 10 wells exhibited low losses (34 cm⁻¹) and low threshold current densities at infinite cavity length (1020 A·cm⁻² and 1190 A·cm⁻², respectively).     

GaAs、GaP、InP、InGaAsP、AlGaAs、InAlGaAs的化学腐蚀研究

为研制全集成光开关、微片式激光器等，对ＧａＡｓ、ＧａＰ、ＩｎＧａＡｓＰ、ＩｎＡＩＧａＡｓ、ＡｌＧａＡｓ等材料的化学腐蚀进行了实验研究。为了研制ＩｎＡｌＧａＡｓ／ＩｎＡｌＡｓ／ＩｎＡｌＧａＡｓ微片式激光器，开发了Ｈ３ＰＯ４／Ｈ２Ｏ２／Ｈ２Ｏ薄层腐蚀液和ＨＣｌ／Ｈ２Ｏ选择性腐蚀液；为了研制ＩｎＧａＡｓＰ／ＩｎＰ／ＩｎＧａＡｓＰＴｂａｒ型光波导，开发了ＨＣｌ／Ｈ３ＰＯ４／Ｈ２Ｏ２薄层腐蚀液和ＨＣｌ／Ｈ２Ｏ２选择性腐蚀液；为了研制ＧａＰ、ＩｎＧａＰ光波导，开发了ＨＣｌ／ＨＮＯ３／Ｈ２Ｏ薄层腐蚀液。它们都具有稳定、重复性好、速率可控、腐蚀后表面形貌好等特点。除此之外，蚀刻成的ＧａＰ光波导侧壁平滑无波纹起伏。此种结果尚未见报导。     

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors

Zn diffusion into InP was carried out ex-situ using a new Zn diffusion technique with zinc phosphorus particles placed around InP materials as zinc source in a semi-closed chamber formed by a modified diffusion furnace.The optical characteristics of the Zn-diffused InP layer for the planar-type InGaAs/InP PIN photodetectors grown by molecular beam epitaxy (MBE) has been investigated by photoluminescence (PL) measurements.The temperature-dependent PL spectrum of Zn-diffused InP samples at different diffusion temperatures showed that band-to-acceptor transition dominates the PL emission,which indicates that Zn was commendably diffused into InP layer as the acceptor.High quality Zn-diffused InP layer with typically smooth surface was obtained at 580 ℃ for 10 min.Furthermore,more interstitial Zn atoms were activated to act as acceptors after a rapid annealing process.Based on the above Zn-diffusion technique,a 50μm planar-type InGaAs/InP PIN photodector device was fabricated and exhibited a low dark current of 7.73 pA under a reverse bias potential of-5 V and a high breakdown voltage of larger than 41 V (I ＜ 10 μA).In addition,a high responsivity of 0.81 A/W at 1.31 μm and 0.97 A/W at 1.55 μm was obtained in the developed PIN photodetector.     

Investigation and optimization of InGaAs/InP heterointerfaces grown by chemical beam epitaxy using spectroscopic ellipsometry and photoluminescence

Spectroscopic ellipsometry (SE) has been used to investigate transition layers for InGaAs/InP heterointerfaces. For the case of InGaAs on InP, we have found that the samples can be best modeled by a strained In_xGa_1-xAs film with the possible presence of a thin interface region (15Å). We are unable to conclusively determine the existence of such a thin transition region. For InP on InGaAs, we find clear indications of As contamination in the bulk film, and that the addition of a thin interface region of In_0.75Gao_0.25As_0.5P_0.5 improves both the numerical fit and shape of the dielectric response curves, especially around E₁ and E₁ + Δ₁ where the effects of a transition region are most pronounced. However, difficulties in modeling the dielectric response of the contaminated InP film make identification of an interface transition region only speculative at this point. Multiple single quantum well structures have also been grown and analyzed with 7K photoluminescence. The quality of the quantum wells shows strong dependence on the gas switching sequence used at the heterointerfaces. The best switching sequence produced a 0.5 nm well with a 7K FWHM of only 12.3 meV. Multiple quantum wells have also been grown to investigate the uniformity and repeatability of our system. Twenty period MQWs with a well width of 1.6 nm display a 14K FWHM of 7.9 meV.     

InGaAsP／InP异质结构材料组分及结构的XPS测定

采用Ｘ射线光电子能谱（ＸＰＳ）对ＩｎＧａＡｓＰ／ＩｎＰ异质结构ＭＯＣＶＤ外延晶片作了表面薄层元素、组分定性、定量和深度分布分析。利用ＸＰＳ组分定量数据与带隙和组分量数据与晶体常数的经验公式计算带隙、晶格常数和失配率，并与光压谱（ＰＶＳ）测定的带隙值和Ｘ射线双晶衍射（ＤＣＤ）测定的失配率作了比较，比较结果是满意的。实验和分析表明，在研究ＭＯＣＶＤ外延膜材料表面组分和表面点阵结构方面。     

InGaAs/InP界面控制对InGaAs薄膜电学和光学性质 的影响

研究了全固态源分子束外延(MBE)生长InGaAs/InP异质结界面扩散对InGaAs外延薄膜电学和光学性质的影响.通过X射线衍射、变温霍尔测试和变温光致发光等方法对InGaAs薄膜样品进行细致研究.发现在InGaAs/InP界面之间插入一层利用As_4生长的InGaAs过渡层,能够显著改善上层InGaAs(利用As_2生长)外延薄膜的电学性能,其低温迁移率显著提高.同时荧光峰反常蓝移动消失,光学性质有所改善.研究表明利用As_4生长InGaAs过渡层,可显著降低As在InP中反常扩散,获得陡峭的InGaAs/InP界面,从而提高InGaAs材料电学和光学性能.     

Optimization of the spacer layer thickness in AlInAs/InGaAs/InP MODFETs

The effects of spacer layer thickness variations on single atomic planar doped (APD) AlInAs/InGaAs modulation doped field effect transistors grown by solid source molecular beam epitaxy have been studied and characterized. The thickness of the AlInAs spacer layer was varied between 0 and 100Å. Room temperature Hall measurements found the mobility exhibited an exponential relationship ranging from 6500 to 10800 cm²/Vs. The sheet charge varied linearly from 3.46 × 10¹² cm^?2 to 2.24 × 10¹² cm^?2. An optimum spacer layer thickness based on maximum channel conductance was found to be 40Å with a mobility of 9600 cm²/Vs and a sheet charge of 3.0 × 10¹² cm^?2. The loss of mobility due to remote ion scattering was examined. This loss was related to the distribution of the Si atoms in the atomic planar doped layer in order to obtain the standard deviation of the interface. This relationship will allow various growth parameters, such as substrate temperature, growth rate, and V/III ratio to be altered to determine the optimum conditions independent of the growth chamber used to create the structures.     

Self-organization phenomenon of strained InGaAs on InP (311) substrates grown by metalorganic vapor phase epitaxy

We have demonstrated that a self-organization phenomenon occurs in strained InGaAs system on InP (311) substrates grown by metalorganic vapor phase epitaxy. This suggests that a similar formation process of nanocrystals exists not only on the GaAs (311)B substrate but also on the InP (311)B substrate. However, the ordering and the size homogeneity of the self-organized nanocrystals are slightly worse than those of the InGaAs/AlGaAs system on the GaAs (311)B substrate. The tensilely strained condition of a InGaAs/InP system with growth interruption in a PH₃ atmosphere reveals a surface morphology with nanocrystals even on the InP (100) substrate. It was found that strain energy and high growth temperature are important factors for self-organization on III-V compound semiconductors. Preliminary results indicate that the self-organized nanostructures in strained InGaAs/InP systems on InP substrates exhibit room temperature photoluminescent emissions at a wavelength of around 1.3 p.m.     

Optimization of the base electrode for InGaAs/InP DHBT structures with a buried emitter-base junction

We have optimized the base electrode for InGaAs/InP based double heterojunction bipolar transistors with a buried emitter-base junction. For the buried emitter-base structure, the base metal is diffused through a thin graded quaternary region, which is doped lightly n-type, to make ohmic contact to the p⁺InGaAs base region. The metal diffusion depth must be controlled, or contact will also be made to the collector region. Several metal schemes were evaluated. An alloy of Pd/Pt/Au was the best choice for the base metal, since it had the lowest contact resistance and a sufficient diffusion depth after annealing. The Pd diffusion depth was easily controlled by limiting the thickness to 50?, and using ample Pt, at least 350?, as a barrier metal to the top layer of Au. Devices with a 500? base region show no degradation in dc characteristics after operation at an emitter current density of 90 kA/cm² and a collector bias, V_CE, of 2V at room temperature for over 500 h. Typical common emitter current gain was 120. An f_t of 95 GHz and f_max, of 131 GHz were achieved for 2×4 μm² emitter size devices.     

InP/InGaAsP脊波导的单模特性与偏振特性研究

以InP/InGaAsP脊形波导结构为研究对象,采用有限元算法(FEM),系统地仿真分析了在固定芯层厚度的情况下,不同脊高和脊宽条件下脊形波导的单模特性和偏振特性.在芯层厚度一定的情况下,脊宽越窄,刻蚀深度越浅,波导的传输模式越接近单模.在深刻蚀情况下,脊波导模双折射系数受到脊宽的影响较大,波导的偏振不敏感性较差;在浅刻蚀情况下,模双折射系数(△n=nTE-nTM)受到脊宽和脊高的影响较为微弱,稳定在1.2×10-3.相关仿真和分析为基于InP/InGaAsP脊波导的光电子器件的结构设计提供了一定的理论支持.     

Critical thickness of GaAs/InGaAs and AlGaAs/GaAsP strained quantum wells grown by organometallic chemical vapor deposition

In this paper we describe a study of strained quantum wells (QWs) as a means to experimentally observe the critical thickness (h _c) for the formation of interfacial misfit dislocations. Two material systems were investigated: GaAs/In_0.11Ga_0.89As, in which the QW layers are under biaxialcompression, and Al_0.35Ga_0.65As/GaAs_0.82P_0.18, in which the QW layers are under biaxialtension. Samples were grown by atmospheric pressure organometallic chemical vapor deposition, and characterized by low-temperature photoluminescence (PL), x-ray diffraction, optical microscopy, and Hall measurements. For both material systems, the observed onset of dislocation formation agrees well with the force-balance model assuming a double-kink mechanism. However, overall results indicate that the relaxation is inhomogeneous. Annealing at 800–850° C had no significant effect on the PL spectra, signifying that even layers that have exceededh _c and have undergone partial relaxation are thermodynamically stable against further dislocation propagation.     

A comparative study of metamorphic InP/InGaAs double heterojunction bipolar transistors with InP and InAIP buffer layers grown by molecular beam epitaxy

We present a comparison of material quality and device performance of metamorphic InGaAs/InP heterojunction bipolar transistors (HBTs) grown by molecular beam epitaxy (MBE) on GaAs substrates with two different types of buffer layers (direct InP and graded InAlP buffers). The results show that the active layer of InP-MHBT has more than one order of magnitude more defects than that of the InAlP-MHBT. The InAlP-MHBTs show excellent direct current (DC) performance. Low DC current gain and a high base junction ideality factor from the InP-MHBT are possibly due to a large number of electrically active dislocations in the HBT active layers, which is consistent with a large number of defects observed by cross-sectional transmission electron microscopy (TEM) and rough surface morphology observed by atomic force microscopy (AFM).     

Temperature,thickness, and interfacial composition effects on the absorption properties of (Hg,Cd)Te epilayers grown by liquid-phase epitaxy on CdZnTe

Transmission spectra of liquid-phase epitaxy (LPE) Hg_1-xCd_xTe with Cd mole fractions in the range of 0.23<x<0.30 have been obtained as a function of temperature and thickness. The results are described using a model consisting of exponential (Urbach) absorption in the band tail region and band-to-band absorption, predicted by a Kane k p model, for the above band gap region. Modifications to the Urbach and transmission expressions are found to be necessary to properly describe the shape, temperature, and thickness dependence of the spectra. A known composition gradient was found to be sufficient to describe the spectra obtained for thin (<20-μm) samples.     

Suppression of extension of the photo-sensitive area for a planar-type front-illuminated InGaAs detector by the LBIC technique

To suppress the extension of the photo-sensitive area of a planar-type InGaAs detector, the structure of the detector was modified, and the small-diffusion-area diffusion method, circle-type covering contact and guard-ring were introduced. The laser-beam-induced-current (LBIC) technique was used to study the photo responsive characteristics of the photo-sensitive area of different detector structures. It was indicated that, by modifying the size of the diffusion area, the width of the circle-type covering contact, the distance between the guard-ring and the photo-sensitive area and the working status of the guard-ring, extension of the photo-sensitive area could be effectively suppressed, and the detector photo-sensitive area could be exactly defined.     

平面型正照射InGaAs探测器光敏面扩大抑制技术的LBIC研究

通过对平面型正照射铟镓砷器件的结构设计,引入小扩散孔扩散、环形遮盖电极、保护环结构抑制器件有效光敏面扩大现象,对器件光敏面进行定义,利用激光诱导电流检测(LBIC)技术研究了不同结构器件光敏面的光响应特性。研究结果表明,通过调节扩散孔尺寸、环形遮盖电极宽度、保护环距离光敏面距离、保护环工作状态等因素可以有效抑制器件有效光敏面扩大现象,对器件光敏面进行精确定义。     

Raman scattering study of the immiscible region in InGaAsP grown by LPE on (100) and (111) GaAs

We have studied the asymmetric broadening of the Raman spectra of In_xGa_1-xAs_yP_1-y grown on GaAs substrates by means of the spatial correlation model. The broadening phenomena was found to be enhanced in the region of immiscibility, in agreement with PL observations. In Raman measurements, the broadening is more enhanced in the samples grown on (100) substrates than in the samples grown on (111) substrates. The enhancement is attributed to the immiscibility included in the samples grown on (100) substrate.     

Influence of mismatch of the lattice parameters on the structural, optical, and transport properties of InGaAs layers grown by molecular beam epitaxy on InP(100) substrates

The influence of mismatch stress on the structural, optical, and transport properties of thick InGaAs layers grown on InP(100) substrates by molecular-beam epitaxy is investigated. It is found that layers having tensile stress can be grown with a greater mismatch than compressively stressed layers before plastic relaxation sets in. The critical mismatch for thick InGaAs layers is not described with sufficient accuracy by either the mechanical equilibrium model or the energy balance model. The range of mismatches required to obtain high carrier mobilities and high radiative recombination efficiencies in InGaAs layers grown on InP substrates is much narrower than the pseudomorphic growth range. The maximum mobilities and minimum widths of the photoluminescence peak are attained in layers matched with the substrate in terms of the lattice parameter and also in slightly gallium-enriched layers. The compositional dependence of the width of the band gap is investigated with allowance for the influence of stress. Fiz. Tekh. Poluprovodn. 31, 19–22 (January 1997)