中红外GaInAsSb PIN多结光伏探测器设计与数值模拟

从非平衡载流子的扩散 -复合理论出发 ,提出 PIN多结探测器材料结构 ,并建立了理论模型进行定量计算 ,从理论上解决了不能同时兼顾增大量子效率与光电增益和降低噪声的矛盾。利用该模型对 Ga In As Sb材料体系作了数值模拟 ,单结器件性能的计算值和实测值基本吻合 ,并根据多结器件模拟结果设计了工作于2 .4μm波段的 Ga In As Sb PIN多结材料结构     

Effect of carrier recombination mechanisms on the open circuit voltage of n^＋-p GaInAsSb thermophotovoltaic cells

By analyzing the main recombination mechanisms in GaInAsSb materials, the dependences of the dark current density and open circuit voltage in n+-p GaInAsSb thermophotovoltaic cells on the recombination parameters, carrier concentration and cell thickness are calculated. The results show that the dark current mainly comes from p-region, and it is related with the surface and Auger recombinations in low and high carrier concentration ranges, respectively. The surface and Auger recombinations can b...     

Spectral response of n+-n-p and n+-p photodiodes

Results of calculations for the quantum efficiency of three different types of n⁺-p, n⁺-n-p, and OCI-HLE diodes are reported. Exact numerical modeling of current density equations, modified to include bandgap reduction and Auger recombination is used to compute the quantum efficiency of these diodes. It is found that an optimized n⁺-p structure can result in over all spectral response comparable to the n⁺-n-p structure, although it is not as good as that of the OCI-HLE type of diodes. Further, these calculations show that one can achieve low dark current in these diodes, but at the expense of lower quantum efficiency particularly for wavelengths less than 0.4 µm.     

n+-p-p+structure InP solar cells grown by organometallic vapor-phase epitaxy

The fabrication of n⁺-p-p⁺InP solar cells by OMVPE has been studied. A conversion efficiency (active area) as high as 20 percent under AM1.5 illumination has been obtained. It is experimentally verified that the n⁺-p-p⁺InP solar cell has a higher resistance to radiation degradation than the n⁺-p InP solar cell. Diode characteristics and photovoltaic performances such as saturation current density, diode-ideality factor, and open-circuit voltage for the n⁺-p-p⁺cells are found to drastically deteriorate when junction depth decreases to ≤ 0.15 µm. An electron concentration dependence of a hole diffusion length in n-InP is estimated from the measurement of photoluminescence spectra. For the improvement of photovoltaic performances, a series of systematic examinations has been made on the relationship between collection efficiency and hole diffusion length from photogenerated carrier distribution analysis.     

Spectral response limitation mechanisms of a shallow junction n+-p photodiode

Modulated monochromatic visible light at various wavelengths was used to generate photocurrent in a silicon n⁺-p diffused diode. A numerical model which includes electric field, heavy doping bandgap reduction, and doping level mobility dependence was used with fitting techniques to determine the carrier lifetime in the n⁺-region at each wavelength. From these measurements it was concluded that the physical mechanisms involved in limiting the spectral response of the n⁺-p photodiode at short wavelengths (0.42 µm) is due to heavy recombination of photogenerated carriers in the n⁺-region. The latter is caused by the heavy doping which results in a fraction of a nanosecond minority carrier lifetime and a retarding or reduced electric field in the n⁺-region. Surface recombination velocity has little influence on this loss mechanism.     

Nonequilibrium behavior of depletion, inversion, and accumulation grain boundaries

The recombination velocity of polysilicon grain boundaries is calculated from the Shocley-Read-Hall formula, taking into account the balance of charges for nonequilibrium conditions. The calculation is not restricted to grain boundaries in depletion, but applies to the full range of band bending. The results show the existence of significant differences in the nonequilibrium behavior of depletion, inversion, and accumulation grain boundaries. For depletion/inversion grain boundaries, the recombination velocity is small and nearly independent of excitation for both low- and high-state densities, whereas medium-state densities show high recombination velocities and a strong injection dependence. Accumulation grain boundaries always provide lower recombination velocities than depletion/inversion grain boundaries and they do not show any dependence upon excitation. In order to verify the theoretical excitation dependences, several n⁺-p and p⁺-n solar cells prepared from polycrystalline bulk material have been investigated under various insolation conditions. For the n⁺-p cells, deviations from a linear dependence of the short circuit current upon intensity were observed, whereas the p⁺-n cells showed a precisely linear dependence, indicating depletion/inversion grain boundaries in p-type, but accumulation grain boundaries in n-type polysilicon.     

Optimization of the germanium preamorphization conditions forshallow-junction formation

Shallow p⁺-n and n⁺-p junctions were formed in germanium preamorphized Si substrates. Germanium implantation was carried out over the energy range of 50-125 keV and at doses from 3×10¹⁴ to 1×10¹⁵ cm^-2. p ⁺-n junctions were formed by 10-keV boron implantation at a dose of 1×10¹⁵ cm^-2. Arsenic was implanted at 50 keV at a dose of 5×10¹⁵ cm^-2 to form the n⁺-p junctions. Rapid thermal annealing was used for dopant activation and damage removal. Ge, B, and As distribution profiles were measured by secondary ion mass spectroscopy. Rutherford backscattering spectrometry was used to study the dependence of the amorphous layer formation on the energy and dose of germanium ion implantation. Cross-sectional transmission electron microscopy was used to study the residual defects formed due to preamorphization. Complete elimination of the residual end-of-range damage was achieved in samples preamorphized by 50-keV/1×10¹⁵ cm^-2 germanium implantation. Areal and peripheral leakage current densities of the junctions were studied as a function of germanium implantation parameters. The results show that high-quality p⁺-n and n⁺-p junctions can be formed in germanium preamorphized substrates if the preamorphization conditions are optimized     

Characterization of shallow silicided junctions for sub-quartermicron ULSI technology. Extraction of silicidation induced Schottkycontact area

The current-voltage (I-V) characteristics of shallow silicided p ⁺-n and n⁺-p junctions are presented. In the former the diode behavior was same as in nonsilicided junction, while drastic change in diode I-V was observed in the latter. The formation of Schottky contact was conclusively shown to be the root cause of the modified I-V behavior of n⁺-p junction in the forward bias region. Poole-Frenkel barrier lowering predominantly influenced the reverse leakage current, masking thereby the effect of Schottky contact. The leakage current in n⁺-p diodes was higher than in nonsilicided diodes by two orders of magnitude and this is consistent with the formation of Schottky contact via titanium or titanium-silicide penetrating into the p-substrate and generating trap sites. There is no increase in the leakage current and no formation of Schottky contact in case of the p⁺-n junction. The Schottky contact amounting to less than 0.01% of the total junction area and not amenable for SEM or TEM observation was extracted for the first time by simultaneous characterization of forward and reverse characteristics of silicided n ⁺-p diode     

俄歇复合对同质结InGaAs探测器探测率的影响

通过对InGaAs材料的俄歇(Auger)复合机制的理论分析,给出了少子寿命与材料组分、温度和载流子浓度的关系,从而得到材料参数等对InGaAs探测器的探测率影响的结果,优化材料参数和器件结构可抑制Auger复合机制,提高InGaAs探测器的探测率.     

Formation of 0.05-μm p+-n and n+-pjunctions by very low (<500 eV) ion implantation

The current-voltage (I-V) characteristics of ultrashallow p⁺ -n and n⁺-p diodes, obtained using very-low-energy (<500-eV) implantation of B and As, are presented. the p⁺-n junctions were formed by implanting B⁺ ions into n-type Si (100) at 200 eV and at a dose of 6×10¹⁴ cm^-2, and n⁺-p junctions were obtained by implanting As⁺ ions into p-type (100) Si at 500 eV and at a dose 4×10¹² cm^-2. A rapid thermal annealing (RTA) of 800°C/10 s was performed before I-V measurements. Using secondary ion mass spectrometry (SIMS) on samples in-situ capped with a 20-nm ²⁸Si isotopic layer grown by a low-energy (40 eV) ion-beam deposition (IBD) technique, the depth profiles of these junctions were estimated to be 40 and 20 nm for p⁺-n and n⁺-p junctions, respectively. These are the shallowest junctions reported in the literature. The results show that these diodes exhibit excellent I-V characteristics, with ideality factor of 1.1 and a reverse bias leakage current at -6 V of 8×10^-12 and 2×10^-11 A for p⁺-n and n⁺-p diodes, respectively, using a junction area of 1.96×10^-3 cm²     

Formation of TiSi2 and shallow junction byAs+ ion-beam mixing and infrared rapid heat treatment

A technique for forming shallow junctions with low-resistance silicide contacts developed for the use in VLSI with scaled MOSFETs is discussed. The salicide (self-aligned silicide) MOSFET gate and source-drain features self-aligned refractory metal silicide and are isolated from one another even without any insulating spacer on the gate sides. A critical step in such a MOSFET fabrication process is the ion implantation through metal silicidation technique, which includes As⁺ ion-beam-induced titanium-silicon interface mixing and infrared rapid heat treatment to form simultaneously the n⁺-p junction and a high-quality TiN covered TiSi₂ contact layer     

一种新颖的HgCdTe光伏探测器R0和Cd测量方法

把碲镉汞(HgCdTe)光伏探测器的零偏压结电阻尺.和结电容Cd的交流测试法与124A型锁相放大器的特点结合起来,提出了一种新颖的R0和Cd测量方法.该方法简单易行,而且能准确测量出高阻(R0≥1kQ)HgCdTe光伏探测器的零偏压结电阻R0、结电容Cd、响应时间τ面阻抗(R0A)等参数,并采用标准探测器估算出该系统的...     

Growth of GaxIn1−xAs1−ySby alloys by metalorganic chemical vapor deposition

The quaternary GaInAsSb alloy system with direct band gaps adjustable in wavelength from 1.7 to 4.3 μm, which may provide the basis for emitters and detectors over this entire region, was studied. Alloys of GaInAsSb were grown lattice-matched on GaSb substrates by metalorganic chemical vapor deposition using a conventional atmospheric pressure horizontal reactor. The properties of the GalnAsSb alloys were characterized by single crystal x-ray rocking curves, the double crystal x-ray rocking curves, the photoluminescence and infrared absorption. A preliminary study of the capabilities of scanning electron acoustic microscopy in the characterization of GaInAsSb alloy has been made, some observations are briefly compared with scanning electron microscopy.     

Mo- and Ti-silicided low-resistance shallow junctions formed using the ion implantation through metal technique

Mo-and Ti-silicided junctions were formed using the ITM technique, which consists of ion implantation through metal (ITM) to induce metal-Si interface mixing and subsequent thermal annealing. Double ion implantation, using nondopant ions (Si or Ar) implantation for the metal-Si interface mixing and dopant ion (As or B) implantation for doping, has resulted in ultrashallow ( ≤ 0.1-µm) p⁺-n or n⁺-p junctions with ∼30-Ω sheet resistance for Mo-silicided junctions and ∼5.5-Ω sheet resistance for Ti-silicided junctions. The leakage current levels for the Mo-silicided n⁺-p junctions (0.1-µm junction depth) and the Mo-silicided p⁺-n junction (0.16-µm junction depth) are comparable to that for unsilicided n⁺-p junction with greater junction depth ( ∼0.25 µm).     

1-2 micron (Hg, Cd)Te photodetectors

The performance of mercury cadmium telluride detectors in the 1-2 micron spectral region has been predicted from basic material parameters. Photovoltaic devices should be characterized by specific responsivities of 1 A/W for a 1000 ohm load when transit time limited to less than 20 ns. Photoconductive detectors made from n-type material should have radiative lifetimes of 1 ms. The feasibility of high performance 1-2 micron (Hg, Cd)Te detectors has been demonstrated experimentally. Deep junction devices operating at room temperature without bias have been fabricated by impurity indiffusion. Detectivities at 1.75 microns approached 10¹⁰cm.Hz^1/2/W with open-circuit responsivities of approximately 500 V/W. In addition, 1.5 micron detectors have been fabricated from p-type, 25 Ω.cm material. With no bias at room temperature, these detectors showed D* λ>10¹⁰cm.Hz/12/W, open-circuit responsivities in excess of 10³V/W, and response times on the order of microseconds. These preliminary results indicate that detectors fabricated from the pseudobinary alloy of (Hg, Cd)Te are well suited for high speed, near infrared photodetection in which room temperature operation is required.     

Band-to-band auger effect in long wavelength multinary III-V alloy semiconductor lasers

Band-to-band Auger effects and radiative recombination rates are theoretically compared for long wavelength multinary III-V compound semiconductor lasers. Stern's band model and matrix element are used for the calculation of gain coefficient and radiative recombination rate. Overlap integrals for Auger processes are obtained by ak cdot pperturbation method. Approximate statistical weight function is used, which includes the weakly degenerate effect. It is found that the Auger effect involving excited split-off band (CHSH process) is dominant when bandgap Egis greater than split-off gap Δ, while the Auger effect involving excited conduction band (CHCC process) predominates over others whenE_{g} < Delta. When Egis comparable to or slightly larger than Δ, the total Auger effect is weak and the quantum efficiency is recovered. This explains the experimentally reported low threshold current in AlGaAsSb and GaInAsSb lasers at about 1.8 μm. In all the possible III-V lasers, the quantum efficiency is reduced to less than 5 percent for wavelengthslambda > 2.2 mum at room temperature and forlambda > 4.4 mum at 77 K, respectively. The calculated values of Auger currents include an error of factor two or three, mainly caused by the ambiguity in band parameters.     

Visible-blindness in photoconductive and photovoltaic AlGaN ultraviolet detectors

The influence of the photodetection mechanism on the performance of AlGaN ultraviolet (UV) detectors is analyzed by studying the characteristics of photoconductors and photovoltaic Schottky diodes fabricated on the same samples. The photoconductive response below the bandgap is not a direct function of the absorption coefficient. Instead, it is amplified by the dominant photoconductive responsivity mechanism, which is attenuated as the chopping frequency increases. On the contrary, photovoltaic detectors are characterized by a sharp UV/visible contrast, mainly dependent on the absorption properties of the material. Thus, these detectors are more suitable for selective UV applications, such as ozone layer monitoring or flame detection.     

论高工作温度碲镉汞红外探测器（下）

与用其他材料制备的红外光子探测器相比,碲镉汞红外探测器具有带隙灵活可调、量子效率较高以及R_oA接近理论值等优点。碲镉汞探测器的主要缺点是需要低温制冷,以抑制引起噪声的热生自由载流子。期望碲镉汞探测器在具有高工作温度(High Opeating Temperature,HOT)的同时而又无需牺牲性能。HOT碲镉汞探测器的设计目标主要是抑制俄歇过程,从而降低探测器噪声和低温制冷需求。从相关基本概念出发,讨论了对HOT碲镉汞物理机制的理解以及近年来HOT碲镉汞技术的发展状况。     

Effects of impurity compensation on injection current in Si bipolar transistors

Experiments were performed on n⁺-p-n and p⁺-n⁺-p transistors to examine the effect of boron impurity compensation on the hole current injected into the heavily arsenic-doped n-type silicon. The result shows that the impurity compensation significantly enhances the hole current only at low temperature, and has little effect at room or higher temperatures.     

Zener current contribution to the resistance-area product of 8- to 14-µm Hg1-xCdxTe photodiodes

The effect of Zener current, due to the internal field emission in the space-charge region of an n⁺-p junction, on the zero-bias resistance-area product RoA of narrow-bandgap HgCdTe photodiodes has been investigated theoretically. It is shown that the contribution of this mechanism in these photodiodes could appreciably lower the RoA product in the temperature range of 10 to 100 K.