Comparative investigation of InP/InGaAs abrupt, setback, and heterostructure-emitter heterojunction bipolar transistors

In this paper, the characteristics of InP/InGaAs abrupt, setback, and heterostructure-emitter heterojunction bipolar transistors (HBTs) are comparatively investigated by twodimensional simulation analysis. In the setback (heterostructure-emitter) HBT, a thin 50 ? undoped In_0.53Ga_0.47As (n-In_0.53Ga_0.47As) layer is inserted between n-InP emitter and p ⁺-InGaAs base layers to lower the energy band at emitter side for decreasing the collector-emitter offset voltage. The simulated results exhibits that the abrupt HBT has the largest current gain, the largest collector-emitter offset voltage, and the smallest unity gain cutoff frequency. While, the setback and heterostructure-emitter HBTs exhibit the smallest current gain and offcet voltage, respectively. Consequentially, the demonstration and comparison of the three-type HBTs provide a promise for design in circuit applications.     

Comparative investigation of InP/InGaAs heterostructure-emitter tunneling and superlattice bipolar transistors

In this article, the characteristics of InP/InGaAs heterostructure-emitter bipolar transistors with 30 n-InP layer tunneling layers and a five-period InP/InGaAs superlattice are demonstrated and comparatively investigated by experimentally results and analysis. In the three devices, a 200 Å n-In_0.53Ga_0.47As layer together with an n-InP tunneling emitter layer (or n-InP/n-InGaAs superlattice) forms heterostructure emitter to decrease collector-emitter offset voltage. The results exhibits that the largest collector current and current gain are obtained for the tunneling transistor with a 30 Å n-InP tunneling emitter layer. On the other hand, some of holes injecting from base to emitter will be blocked at n-InP/n-InGaAs heterojunction due to the relatively small hole transmission coefficient in superlattice device, which will result in a considerable base recombination current in the n-InGaAs layer. Therefore, the collector current and current gain of the superlattice device are the smallest values among of the devices.     

Evaluation of magnesium and manganese as the P-type dopant for InP/InGaAs heterojunction transistors

Among Zn, Cd, Mg, Mn, and Be as the p-type dopant in InGaAs, Mg and Mn were taken as candidates for the dopant in the base region of InP/InGaAs heterojunction transistors. Properties of the two dopants were investigated in terms of doping reproducibility, diffusion in solid phase, and attainable optical gain in the InP/InGaAs heterojunction phototransistors. Mn was found to be suitable for the p-type dopant in the InGaAs base region of InP/InGaAs n-p⁺-n transistors.     

A comparison of TMGa and TEGa for low-temperature metalorganic chemical vapor deposition growth of CCI4-doped inGaAs

Factors which influence the alloy composition and doping level of CCl₄-doped In_0.53Ga_04.7As grown at low temperatures (450°C < T_g < 560°C) by low-pressure metalorganic chemical vapor deposition (MOCVD) have been investigated. The composition is highly dependent on substrate temperature due to the preferential etching of In from the surface during growth and the temperature-dependent growth efficiency associated with the Ga source. The lower pyrolysis temperature of TEGa relative to TMGa allows the growth of CCl₄-doped InGaAs at lower growth temperatures than can be achieved using TMGa, and results in improved uniformity. High p-type doping (p ∼ 7 × 10¹⁹ cm^-8) has been achieved in C-doped InGaAs grown at T = 450°C. Secondary ion mass spectrometry analysis of a Cdoping spike in InGaAs before and after annealing at ∼670°C suggests that the diffusivity of C is significantly lower than for Zn in InGaAs. The hole mobilities and electron diffusion lengths in p⁺-InGaAs doped with C are also found to be comparable to those for Be and Zn-doped InGaAs, although it is also found that layers which are highly passivated by hydrogen suffer a degradation in hole mobility. InP/InGaAs heterojunction bipolar transistors (HBTs) with a C-doped base exhibit high-frequency performance (f_t = 62 GHz, f_max=42 GHz) comparable to the best reported results for MOCVD-grown InP-based HBTs. These results demonstrate that in spite of the drawbacks related to compositional nonuniformity and hydrogen passivation in CCl₄-doped InGaAs grown by MOCVD, the use of C as a stable p-type dopant and as an alternative to Be and Zn in InP/ InGaAs HBTs appears promising.     

Comparison of heterostructure-emitter bipolar transistors (HEBTs) with InGaAs/GaAs superlattice and quantum-well base structures

The characteristics of InGaP/GaAs heterostructure-emitter bipolar transistors (HEBTs) including conventional GaAs bulk base, InGaAs/GaAs superlattice-base, and InGaAs quantum-well base structures are presented and compared by two-dimensional simulation analysis. Among of the devices, the superlattice-base device exhibits a highest collector current, a highest current gain and a lowest base–emitter turn-on voltage attributed to the increased charge storage of minority carriers in the InGaAs/GaAs superlattice-base region by tunneling behavior. The relatively low turn-on voltage can reduce the operating voltage and collector–emitter offset voltage for low power consumption in circuit applications. However, as to the quantum-well base device, the electrons injecting into the InGaAs well are blocked by the p⁺-GaAs bulk base and it causes a great quantity of electron storage within the small energy-gap n-type GaAs emitter layer, which significantly increases the base recombination current as well as degrades the collector current and current gain.     

Short-wavelength infrared array avalanche photodetectors on the basis of InGaAs heteroepitaxial structures

SWIR ADP 320 × 256 FPAs based on p–i–n photodiodes in InGaAs heterostructures have been developed and investigated. The typical InGaAs/InP PIN heterostructures are formed by Metal Organic Vapor Phase Epitaxy (MOVPE) on n⁺ type InP substrates. The InGaAs/InP PIN photodiodes performance have been estimated by measuring current-voltage characteristics. APD arrays are designed using a mesa-passivated avalanche photodiode device array of p–i–n junctions in heterostructure with common absorption and multiplication regions. The optimal operating point for managing avalanche application depended on various factors has been started at 15 V bias and the multiplication coefficient was of 2–4.     

The structural and electrical properties of the SrTa2O6/In0.53Ga0.47As/InP system

The structural and electrical properties of SrTa₂O₆(SrTaO)/n-In_0.53GaAs_0.47(InGaAs)/InP structures where the SrTaO was grown by atomic vapor deposition, were investigated. Transmission electron microscopy revealed a uniform, amorphous SrTaO film having an atomically flat interface with the InGaAs substrate with a SrTaO film thickness of 11.2 nm. The amorphous SrTaO films (11.2 nm) exhibit a dielectric constant of ∼20, and a breakdown field of >8 MV/cm. A capacitance equivalent thickness of ∼1 nm is obtained for a SrTaO thickness of 3.4 nm, demonstrating the scaling potential of the SrTaO/InGaAs MOS system. Thinner SrTaO films (3.4 nm) exhibited increased non-uniformity in thickness. From the capacitance-voltage response of the SrTaO (3.4 nm)/n-InGaAs/InP structure, prior to any post deposition annealing, a peak interface state density of ∼2.3 × 10¹³ cm⁻² eV⁻¹ is obtained located at ∼0.28 eV (±0.05 eV) above the valence band energy (E_v) and the integrated interface state density in range E_v + 0.2 to E_v + 0.7 eV is 6.8 × 10¹² cm⁻². The peak energy position (0.28 ± 0.05 eV) and the energy distribution of the interface states are similar to other high-k layers on InGaAs, such as Al₂O₃ and LaAlO₃, providing further evidence that the interface defects in the high-k/InGaAs system are intrinsic defects related to the InGaAs surface.     

Hooge parameter of InGaAs bulk material and InGaAs 2DEG quantum well structures based on InP substrates

The 1/f noise of various InGaAs layers lattice matched to InP is investigated systematically at room temperature. To elucidate the origin of the 1/f noise in this type of III–V compound semiconductor, thick n-type doped InGaAs layers, typical InP based InAlAs/InGaAs or InP/InGaAs heterostrucuture field-effect transistor (HFET) structures, respectively, as well as InP based InAlAs/InGaAs quantum well structures with doped InGaAs two-dimensional electron gas (2DEG) channel are analysed. From the experiments it is found that mobility fluctuation is the only origin for the 1/f noise observed both in InGaAs bulk material and in 2DEG heterostructures of high quality. A Hooge parameter attributed to phonon scattering α_Hphon in the bulk material is found to be about 7×10⁻⁶ and agrees with those obtained from HFET structures with the highest mobilities (α_H≈1.5×10⁻⁵). Furthermore, the Hooge parameter of 2DEG structures strongly depends on the channel design and on the doping concentration in the n-type doped 2DEG channels.     

Double-heterostructure InGaAs/InP PIN photodetectors

High-quality n⁺InP/InGaAs/p⁺InP double-heterojunction PIN photodetectors have been grown by special liquid-phase-epitaxial techniques. This development allows front illumination which substantially facilitates device fabrication and operation. Furthermore, good control of pn junction location and layer thickness in these structures permits optimization of high-speed performance. For convenient device areas, low dark-current densities (2.5×10⁻⁵ A/cm²) and short response-times (50 ps) are obtained. High-speed design parameters are discussed, and the reduction of response times to 30 ps is predicted.     

Study of the Formation Mechanism of Cu/Ge/Pd Ohmic Contact to <Emphasis Type="Italic">n</Emphasis>-Type InGaAs

This study investigates electrical characteristics and the formation mechanism of the Cu/Ge/Pd Ohmic contact to n-type InGaAs. After annealing the contact at 250°C for 20 min, Cu₃Ge and Pd₁₂Ga₅As₂ compounds formed and Ge diffused into the InGaAs layer, achieving a heavily doped InGaAs layer with a low contact resistivity of 1 × 10⁻⁶ Ω cm². Thermal stability tests were performed on the Cu/Ge/Pd Ohmic contact to InGaAs after Ohmic contact formation, showing no obvious degradation after a 72 h reliability test at 250°C. The results indicate excellent electrical characteristics and thermal stability using Cu/Ge/Pd as an Ohmic contact metal to an n-InGaAs layer.     

A reliable fabrication technique for very low resistance ohmic contacts top-InGaAs using low energy Ar+ ion beam sputtering

A new fabrication technique for ohmic Au/Pt/Ti contacts top-InGaAs is presented employing anodic oxidization and sputter etching by low energy Ar⁺ ions prior to the metal deposition. This cleaning procedure was found to be superior to wet chemical pre-etching as it provides low resistivity contacts with excellent homogeneity and good uniformity after rapid thermal processing (RTP).     

InGaAsP/InGaAs双结太阳电池研究

本文采用MOCVD设备生长了与InP晶格匹配的InGaAs(P)光伏器件。分析了InGaAsP/InGaAs (1.07/0.74 eV)双结太阳电池的QE与I-V特性。在AM1.5D光谱下,InGaAsP/InGaAs双结太阳电池的开路电压,短路电流,填充因子及转换效率分别为0.977 V, 10.2 mA/cm,80.8%,8.94%。对于InGaAsP/InGaAs双结太阳电池,在聚光条件下,其最大转换效率在280个聚光倍数下达到了13%。这一结果预示了GaInP/GaAs/InGaAsP/InGaAs四结太阳电池的潜在应用前景。     

Tunneling currents in In0.53Ga0.47As homojunction diodes and design of InGaAs/InP hetero-structure avalanche photodiodes

Tunneling currents in InGaAs homojunctions were studied from measurements of temperature dependence of breakdown voltage, current-voltage characteristics, tunneling effective mass, and noise spectrum. Zener emission dominates the reverse current prior to avalanche breakdown in the carrier concentration region of >10¹⁵ cm^?3 and restricts the avalanche gain in InGaAs homojunctions. An InGaAs/InP hetero-structure having a p-n junction in the InP layer was studied to reduce dark currents caused by Zener emission. A design chart to aid in the realization of a high performance APD is discussed.     

The thermal stability of ohmic contact to n-type InGaAs layer

The thermal stability of ohmic contact to n-type InGaAs layer is investigated. When Ni/Ge/Au is used as the contact metal, the characteristics of the ohmic contact are degraded after thermal treatment. The specific contact resistance of (Ni/Ge/Au)-InGaAs ohmic contact after annealing at 450°C is about 15 times larger than that of as-deposited sample. This is due to the decomposition of InGaAs and the interdiffusion of Ga and Au. A new phase of Au₄ln appears after annealing at 300°C. While in the case of Ti/Pt/Au, Au does not penetrate into the InGaAs layer as revealed by secondary ion mass spectroscopy. The specific contact resistance of (Ti/Pt/Au)-InGaAs ohmic contact after annealing at 450°C is eight times larger than that of as-deposited sample. Therefore, the thermal stability of (Ti/Pt/Au)-InGaAs ohmic contact is better than that of (Ni/Ge/Au)InGaAs ohmic contact.     

Zinc-doping of InP during chemical beam epitaxy using diethylzinc

Diethylzinc was used as ap-type dopant source during InP growth by chemical beam epitaxy. In InP, electrically activated Zn saturated at a concentration of ∼2.0 × 10¹⁸ cm⁻³ for epilayers grown at 540‡ C. Higher role concentrations were obtained by lowering the growth temperature. However, measurements with SIMS indicated that very serious Zn diffusion occurred when the Zn concentration appeared to reduce the pyrolysis efficiency of trimethylindium. This caused a reduction in the InP growth rate and InAs mole fraction in InGaAs epilayers. No Zn “memory effect≓ was detected in our system. Undoped InP epilayers maintained an n-type background of ∼5 × 10¹⁵ cm⁻³.     

New tri-state switch (TSS) using AlGaAs/GaAs/InGaAs double heterostructure

A new AlGaAs/GaAs/InGaAs heteroconfinement tri-state switch (TSS) prepared by metal organic chemical vapor deposition has been fabricated and demonstrated. This TSS exhibits the interesting multiple negative differential resistance (MNDR) characteristics. The NDR behavior is caused by a p ⁺ n junction and sequential two-stage barrier-lowering and potential-redistribution effect that resulted from the electron confinement at AlGaAs/GaAs/InGaAs heterointerface and lnGaAs quantum well, respectively.     

Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures

Dislocations and related point defect complexes caused by lattice mismatch currently limit the performance of heteroepitaxial InP cells by introducing shunting paths across the active junction and by the formation of deep traps within the base region. We have previously demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of such defects within heteroepitaxial InP layers. In this work, we present our first results on the hydrogen passivation of ac tual heteroepitaxial n⁺p and p⁺n InP cell structures grown on GaAs substrates by metal organic chemical vapor deposition (MOCVD). We have found that a 2-h exposure to a 13.56-MHz hydrogen plasma at 275°C reduces the deep level co ncentration in the base regions of both n⁺p and p⁺n heteroepitaxial InP cell structures from as-grown values of 5–7 × 10¹⁴ cm⁻³, down to 3–5 × 10¹² cm⁻³. All dopants were successfully reactivated by a 400°C, 5-min anneal with no detectable activation of deep levels. Current-voltage (I-V) analysis indicated a subsequent ∼100-fold decrease in reverse leakage current at 1 V reverse bias, and an impro ved built-in voltage for the p⁺n structures. In addition to being passivated, dislocations are also shown to participate in secondary interactions during hydrogenation. We find that the presence of dislocations enhances hydrogen diffusion into the cell structure and lowers the apparent dissociation energy of Zn-H complexes from 1.19 eV for homoepitaxial Zn-doped InP to 1.12 eV for heteroepitaxial Zn-doped InP. This is explained by additional hydrogen trapping at dislocations subsequent to the r eactivation of Zn dopants after hydrogenation.     

Galvanic corrosion effects in InP-based laser ridge structures

Galvanic corrosion effects in metallized III-V laser structures have been studied. Small gaps present in the metallization can leave exposed semiconductor regions, which are susceptible to localized corrosion in the presence of an electrolyte. Electochemical measurements in two different electrolytes, i.e., 1% HF and concentrated H₃PO₄, were made of test structures comprised of n-type InP, p-type InP, and p-type InGaAs, as well as Au. Polarization measurements were made in all cases relative to a Ag/AgCl reference electrode. Corrosion potentials, measured relative to Au, of 540, 180, and 330 mV were obtained for n-type InP, p-type InP, and p-type InGaAs, respectively, in 1% HF. Values of 415, 47, and 138 mV were obtained for n-type InP, p-type InP, and p-type InGaAs, respectively, in concentrated H₃PO₄. Galvanic current densities of 2.0 × 10⁻⁶A/cm², 1.0 × 10⁻⁷ A/cm², and 4.0 × 10⁻⁶ A/cm² were obtained for galvanic couples of n-type InP/Au, p-type InP/Au, and p-type InGaAs/Au, respectively, in 1%HF. Values of 1.2 × 10⁻⁶ A/cm², 1.2 × 10⁻⁷ A/cm², and 1.0 × 10⁻⁶ A/cm² were obtained for galvanic couples of n-type InP/Au, p-type InP/Au, and p-type InGaAs/Au, respectively, in concentrated H₃PO₄. Complementary microstructural studies, using scanning electron microscopy, were done on actual metallized ridge laser structures, consisting of a p-type InP ridge with a p-type InGaAs capping layer and a Ti/Pt/Au metallization. Localized pitting of the InGaAs layer was observed for samples with gaps in the metallization.     

Passivation of Interfacial States for GaAs- and InGaAs/InP-Based Regrown Nanostructures

The interfacial charge density of regrown structures was studied for several␣different material systems: GaAs, InGaAs/InP, and InAlAs-InGaAs superlattice structures on InP. The particular application of interest is in the␣fabrication of nanoscale devices. Such structures require a very low density of interfacial charge at their exposed surfaces in order to avoid Fermi-level pinning and subsequent lateral carrier depletion across the structure. (110)-Oriented samples, mimicking the exposed sidewalls of nano-etched structures, were plasma-etched using a variety of gas-phase chemistries. The interfacial charge density at regrown interfaces was studied using capacitance–voltage (CV) and electrochemical CV techniques after in situ and ex situ pretreatments and epitaxial regrowth. The minimum interfacial charge densities obtained for these material systems were <10¹¹ cm⁻². Preferential regrowth around etched nanopillars was demonstrated for InP-based structures.     

MBE生长的InP DHBT的性能

报道了一种自对准InP/InGaAs 双异质结双极晶体管的器件性能.成功制作了U型发射极尺寸为2μm×12μm的器件,其峰值共射直流增益超过300,残余电压约为0.16V,膝点电压仅为0.6V,而击穿电压约为6V.器件的截至频率达到80GHz,最大震荡频率为40GHz.这些特性使此类器件更适合于低压、低功耗及高频方面的应用.