First hydride free GaInP/GaAs carbon doped HBT grown by CBE usingDMAAs and TBP

A current gain of 120, for a base sheet resistance of 400 Ω/□, is reported in a carbon doped base heterojunction bipolar transistor grown by chemical beam epitaxy (CBE) without hydride sources. This result is to the authors' knowledge, the best obtained with hydride free CBE for this device     

Comparison of GaInP/GaAs heterostructure-emitter bipolartransistors and heterojunction bipolar transistors

Carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBT's) and heterostructure-emitter bipolar transistors (HEBT's) grown by MOCVD were fabricated. Experimental comparison of HBT's and HEBT's has been made based on the dc and the RF performance. HBT's have higher current gains than those of HEBT's in the high current regime, while HEBT's offer a smaller offset voltage and better uniformity in dc characteristics across the wafer. The current gain and cutoff frequency of the DEBT with a 150 Å emitter set-back layer are comparable to those of HBT's. DC (differential) current gains of 600 (900) and 560 (900) were obtained at a collector current density of 2.5×10⁴ A/cm² for the HBT and HEBT, respectively. The cutoff frequencies are 37 and 31 GHz for the HBT and HEBT, respectively. It is shown that there is negligible contribution of the diffusion capacitance to the emitter capacitance in HEBT's with a thin emitter set-back layer but not with a thick emitter set-back layer. The behavior of HEBT's both in dc and RF characteristics is similar to that of HBT's     

A broad-band amplifier using GaAs/GaAlAs heterojunction bipolartransistors

A compact wideband amplifier (or gain block) designed around a Darlington pair of GaAs/GaAlAs heterojunction bipolar transistors (HBTs) is discussed. This circuit has been fabricated by an ion-implanted process with a transistor f_t of 40 GHz. Two variants of the circuit gave either a 8.5-dB gain with a DC-to-5-GHz 3-dB bandwidth or a 13-dB gain with a DC-to-3-GHz bandwidth. These amplifiers gave 11.8- and 18.3-dBm output, respectively, at 1-dB gain compression     

Heavily doped base GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy

The first demonstration of a GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy is reported. A common-emitter current gain of 30 at a current density of 110 A/cm/sup 2/ is obtained for a beryllium base doping as high as 8*10/sup 19/ cm/sup -3/. The base sheet resistance of 140 Omega / Square Operator is among the lowest reported values.<>     

InP/In0.53Ga0.47As heterojunction bipolartransistors with a carbon-doped base grown by MOCVD

InP/In_0.53Ga_0.47As heterojunction bipolar transistors (HBTs) utilizing a carbon-doped base have been demonstrated. The devices were grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) using carbon tetrachloride (CCl₄) as the p-type dopant source. These devices exhibit a DC common-emitter current gain of 50 and an emitter-base junction ideality factor of 1.29 in a structure for which no undoped spacer layer was employed at the emitter-base junction. These preliminary results suggest that C-doping of In_0.53Ga_0.47As may be a suitable alternative to Zn in MOCVD-grown InP/In_0.53Ga_0.47As HBTs     

Performance enhancement of GaInP/GaAs heterojunction bipolarphototransistors using dc base bias

GaInP-GaAs heterojunction bipolar phototransistors grown by metal organic vapor phase epitaxy (MOVPE) and operated with frontside optical injection through the emitter are reported with high optical gain (<88) and record high frequency performance (28 GHz). Heteropassivation of the extrinsic base surface is employed using a depleted GaInP emitter layer between the nonself-aligned base contact and the emitter mesa. The phototransistor's performance is shown to improve with increasing dc base bias in agreement with predictions of a recently reported Gummel-Poon model. Experimental results are reported for devices with optical active areas of 10×10 μm², 20×20 μm², and 30×30 μm², with peak measured cutoff frequencies of 28.5, 23.1, and 18.5 GHz, respectively, obtained at collector current densities between 2×10 ³ and 6×10³ A/cm²     

A high-frequency GaInP/GaAs heterojunction bipolar transistor withreduced base-collector capacitance using a selective buriedsub-collector

A C-doped GaInP/GaAs HBT using a selective buried sub-collector has been fabricated by two growth steps. The device was fabricated with minimum overlap of the extrinsic base and the sub-collector region to reduce base-collector capacitance. The experiment shows that the base collector capacitance is reduced to about half of that of an HBT without selective buried sub-collector while the base resistance remains unchanged. A current gain of 35, f_T of 50 GHz and f_max of 140 GHz are obtained with this technology     

分子束外延生长的GaAs/GaInP双结电池研究

We report the recent result of GaAs/GaInP dual-junction solar cells grown by all solid-state molecularbeamepitaxy(MBE).The device structure consists of a GaIn0.48P homojunction grown epitaxially upon a GaAs homojunction,with an interconnected GaAs tunnel junction.A photovoltaic conversion efficiency of 27% under the AM1.5 globe light intensity is realized for a GaAs/GaInP dual-junction solar cell,while the efficiencies of 26% and 16.6% are reached for a GaAs bottom cell and a GaInP top cell,respectively.The energy loss mechanism of our GaAs/GaInP tandem dual-junction solar cells is discussed.It is demonstrated that the MBE-grown phosphide-containing Ⅲ–V compound semiconductor solar cell is very promising for achieving high energy conversion efficiency.     

Ultra-shallow np junction formed by PH3 and AsH3 plasma immersion ion implantation

Ultra-shallow 28–88 nm n⁺p junctions formed by PH₃ and AsH₃ plasma immersion ion implantation (PIII) have been studied. The reverse leakage current density and intrinsic bulk leakage current density of the diodes are found to be as low as 4.2 nA cm⁻² and 2.4 nA cm⁻², respectively. The influences of pre-annealing condition and the carrier gas on the junction depth and the sheet resistance are also studied. It is found that the increase of H or He content in the PH₃ PIII can slow down the phosphorus diffusion and shallower junction can been obtained. Annealing conditions have pronounced effect on the sheet resistance. It was found that sample annealed at 850 °C for 20 s has reverse results to that annealed at 900 °C for 6 s. For AsH₃ PIII samples, it is observed that two-step annealing is more effective to activate the dopant and a lower reverse current density resulted.     

Photoluminescence of AlGaAs alloy grown by LP-MOVPE at different temperatures using TBA in N2 ambient

High quality of Al_xGa_1−xAs alloys have been grown by the LP-MOVPE using tertiary-butyl arsine as group V precursor in 100% nitrogen ambient. The photoluminescence (PL) properties of Al_0.25Ga_0.75As alloy grown at different temperature have been studied. The PL peak emission intensity of the samples increases with the substrate growth temperature initially and saturated at the growth temperature 760°C. The emission intensity decreases when further increase the temperature. This is attributed to the oxygen content in the samples.     

Effect of high-temperature annealing on GaInP/GaAs HBT structures grown by LP-MOVPE

We have investigated the effect of high-temperature annealing on device performance of GaInP/GaAs HBTs using a wide range of MOVPE growth parameters for the C-doped base layer. Carbon doping was achieved either via TMG and AsH₃ only or by using an extrinsic carbon source. High-temperature annealing causes degradation of carbon-doped GaAs in terms of minority carrier properties even at doping levels of p=1 × 10¹⁹ cm⁻³. The measured reduction in electron lifetime and luminescence intensity correlates with HBT device results. It is shown that the critical temperature where material degradation starts is both a function of doping method and carbon concentration.     

CH3NH3PbI3/p-Si异质结的光电特性研究

利用一步溶液法在p型Si衬底上生长有机/无机杂化钙钛矿CH3NH3PbI3薄膜,构成CH3NH3PbI3/p-Si异质结。利用原子力显微镜(AFM)、扫描电子显微镜(SEM)对薄膜形貌和结构进行表征,通过无光照和有光照条件下的电流-电压(I-V)、电容-电压(C-V)测试对异质结的光电特性进行研究。I-V测试结果显示CH3NH3PbI3/p-Si异质结具有整流特性,正反偏压为±5V时,整流比大于70,并在此异质结上观察到了光电转换现象,开路电压为10mV,短路电流为0.16uA。C-V测试结果显示Ag/CH3NH3PbI3/p-Si异质结具有与MIS(金属-绝缘层-半导体)结构相似的C-V特性曲线,与理想MIS的C-V特性曲线相比,异质结的C-V曲线整体沿电压轴向正电压方向平移。C-V特性曲线的这种平移表明Ag/CH3NH3PbI3/p-Si异质结界面存在界面缺陷,CH3NH3PbI3层也可能存在固定电荷。这种界面缺陷是导致CH3NH3PbI3/p-Si异质结开路电压的大幅度降低的重要原因。此外,CH3NH3PbI3薄膜的C-V测试结果显示其具有介电非线性特性,其介电常数约为4.64。     

High-speed InGaP/GaAs heterojunction bipolar transistors withburied SiO2 using WSi as the base electrode

High-speed InGaP/GaAs heterojunction bipolar transistors (HBT's) with a small emitter area are described. WSi is used as the base electrode to fabricate HBT's with a narrow base contact width and a buried SiO₂ structure. An HBT with an emitter area of 0.8×5 μm exhibited an f_T of 105 GHz and an f_max of 120 GHz. These high values are obtained due to the reduction of C_BC by using buried SiO₂ with a narrow base contact width, indicating the great potential of GaAs HBT's for high-speed and low-power circuit applications     

A planar-doped 2D-hole gas base AlGaAs/GaAs heterojunction bipolartransistor grown by molecular beam epitaxy

A novel type of AlGaAs/GaAs heterojunction bipolar transistor (HBT) which uses a two-dimensional (2-D) hole gas base formed by planar doping using molecular-beam epitaxy (MBE) has been demonstrated. The base consists of a submonolayer of Be atoms of sheet concentration 0.5-5×10¹³ cm^-2 which is deposited during growth interruption by MBE. The transistor structure exhibits DC current gains up to 700. The effective base transit time is negligible in these transistors and it is postulated that very high-speed nonequilibrium transport may occur in the collector region     

Improvement of Ga2O3 vertical Schottky barrier diode by constructing NiO/Ga2O3 heterojunction

The high critical electric field strength of Ga₂O₃ enables higher operating voltages and reduced switching losses in power electronic devices. Suitable Schottky metals and epitaxial films are essential for further enhancing device performance.In this work, the fabrication of vertical Ga₂O₃ barrier diodes with three different barrier metals was carried out on an n–-Ga₂O₃homogeneous epitaxial film deposited on an n+-β-Ga₂...     

Band offsets of In0.30Ga0.70As/In0.29Al0.71As heterojunction grown on GaAs substrate

Temperature-dependent current-voltage measurement was employed to study the band offsets of the In_0.30Ga_0.70As/In _0.29Al_0.71As heterojunction. The conduction band discontinuity was determined to be 0.71±0.05 eV which corresponds to a conduction band offset to bandgap difference ratio ~0.66. The comparison between experimental and theoretical results is presented     

A low-impedance coplanar waveguide using an SrTiO3 thinfilm for GaAs power MMIC's

A novel structure for coplanar-waveguide transmission lines with low impedance and low loss is demonstrated in this paper. The new structure simply has a high dielectric SrTiO₃ thin film underneath the coplanar conductors. Due to the high dielectric constant of SrTiO₃, the coplanar line exhibited characteristic impedance as low as 18 Ω with a slot width of 5 μm and the center conductor width of 50 μm, while a conventional coplanar line on GaAs showed only 30 Ω with the same configuration. The newly developed coplanar structure is easily applicable for present GaAs monolithic-microwave integrated-circuit (MMIC) technology, especially for power MMIC's and low-impedance devices     

A study of GaAs: Si/GaAs: C tunnel diodes grown by MOCVD

Technological modes in which high-efficiency GaAs: Si/GaAs: C tunneling structures can be fabricated by MOS-hydride epitaxy have been determined. It was demonstrated that use of C and Si dopants makes it possible to obtain a p-n junction with low diffusion spreading of dopant profiles. It was shown that fabrication of high-efficiency tunnel diodes requires that GaAs layers should be doped with acceptor and donor impurities to a level of ∼9 × 10¹⁹ cm⁻³. Tunnel diodes were fabricated using the tunnel structures and their current-voltage characteristics were studied. Peak current densities J _p ≈ 1.53 kA cm⁻² and a differential resistance R ≈ 30 mΩ under a reverse bias were obtained in the tunnel diodes.     

A process for the formation of submicron V-gate by micromachinedV-grooves using GaInP/GaAs selective etching technique

A process for the formation of submicron V-gates by V-grooves was demonstrated for the first time. The fabrication steps of V-gates consist of anisotropic wet etching of the undoped GaAs layer grown on top of a GaInP layer and subsequent metal evaporation and lift-off process. Owing to the outward slope of the sidewalls of the micromachined V-groove, submicron gate length could be easily obtained by normal 1 μm UV photolithography. The submicron V-gate process was also applied successfully to the fabrication of V-gate GaInP/GaAs/InGaAs metal semiconductor field effect transistors with a gate length of 0.6 μm     

Characterization of InGaAs/GaAs(001) films grown by metalorganic vapor phase epitaxy using alternative sources

Thin films of In_xGa_1−xAs (0<x<0.012) on GaAs (001) were grown by metalorganic vapor phase epitaxy using triisopropylindium, triisobutylgallium, and tertiarybutylarsine. The effect of the process conditions, temperature, and V/III ratio on the film quality was studied using high resolution x-ray diffraction, scanning tunneling microscopy, and Hall measurements. High quality films were grown at temperatures as low as 475 °C and at a V/III ratio of 100. However, under these conditions, a change in growth mode from step flow to two-dimensional nucleation was observed.