Admittance spectroscopy of ring diode InGaAs/InAlAs/InP quantum-well structures

The admittance of ring planar diode Au/InGaAs/InP and Au/InGaAs/InAlAs heteronanostructures on i-InP has been studied. The structures are constituted by a silicon ??-doped layer and an InGaAs quantum well (QW) in InP or InAlAs epitaxial layers. An analysis of the capacitance-voltage and conductance-voltage characteristics yielded distribution profiles of the electron concentration and mobility in the vicinity of the QW and ??-doped layer. It is shown that lowering the temperature leads to an increase in the electron concentration and mobility in the QW.     

Effect of Channel Width Shortening on the Stability of a-Si:H/nc-Si:H Bilayer Thin-Film Transistors

The static bias-stress-induced degradation of hydrogenated amorphous/nanocrystalline silicon bilayer bottom-gate thin-film transistors is investigated by monitoring the turn-on voltage (V _on) and on-state current (I _on) in the linear region of operation. Devices of constant channel length 10 mum and channel width varying from 3 to 400 mum are compared. The experimental results demonstrate that the device degradation is channel-width dependent. In wide channel devices, substantial degradation of V _on is observed, attributed to electron injection into the gate dielectric, followed by I _on reduction due to carrier scattering by the stress-induced gate insulator trapped charge. With shrinking the channel width down to 3 mum, the device stability is substantially improved due to the possible reduction of the electron thermal velocity during stress or due to the gate insulator quality uniformity over small dimensions.     

100 nm gate AlGaN/GaN HEMTs on silicon with fT = 90 GHz

The realisation of 0.1 mum gate AlGaN/GaN high electron mobility transistors grown on high-resistivity silicon substrates is reported. A maximum current density of 750 mA/mm and an extrinsic transconductance of 225 mS/mm are achieved. The devices feature a record current gain cutoff frequency as high as f _T=90 GHz, the highest value ever reported from a GaN-based device grown on a silicon substrate. The results demonstrate the great potential of GaN-on-silicon technology for low-cost millimetre-wave applications.     

High Transconductance MISFET With a Single InAs Nanowire Channel

Metal-insulator field-effect transistors (FETs) are fabricated using a single n-InAs nanowire (NW) with a diameter of d = 50 nm as a channel and a silicon nitride gate dielectric. The gate length and dielectric scaling behavior is experimentally studied by means of dc output- and transfer-characteristics and is modeled using the long-channel MOSFET equations. The device properties are studied for an insulating layer thickness of 20-90 nm, while the gate length is varied from 1 to 5 mum. The InAs NW FETs exhibit an excellent saturation behavior and best breakdown voltage values of V _BR > 3 V. The channel current divided by diameter d of an NW reaches 3 A/mm. A maximum normalized transconductance g_m /d > 2 S/mm at room temperature is routinely measured for devices with a gate length of les 2 mum and a gate dielectric layer thickness of les 30 nm.     

60-GHz pseudomorphicAl0.25Ga0.75As/In0.28Ga0.72As low-noise HEMTs

V-band low-noise planar-doped pseudomorphic (PM) InGaAs high electron mobility transistors (HEMTs) were fabricated with an indium mole fraction of 28% in the InGaAs channel. A device with 0.15-μm T-gate achieved a minimum noise figure of 1.5 dB with an associated gain of 6.1 dB at 61.5 GHz     

High-performance In0.52Al0.48As/In0.53Ga0.47As HFET compatible with optical-detectorintegration

The authors report the successful demonstration of a 1.0-μm gate InAlAs/InGaAs heterojunction FET (HFET) on top of thick InGaAs layers using lattice-matched molecular beam epitaxy (MBE). This scheme is compatible with metal-semiconductor-metal (MSM) photodetector fabrication. The authors measured the performance of InAlAs/InGaAs HFETs from 0 to 40 GHz. Device performance is characterized by peak extrinsic transconductances of 390 mS/mm and as-measured cutoff frequencies up to 30 GHz for a nominal 1.0-μm-gate-length HFET. HFET device measurements are compared for samples growth with and without the thick underlying InGaAs optical-detector absorbing layer     

Asymmetrically Recessed 50-nm Gate-Length Metamorphic High Electron-Mobility Transistor With Enhanced Gain Performance

We report the design, fabrication and characterization of ultrahigh gain metamorphic high electron-mobility transistors. In this letter, a high-yield 50-nm T-gate process was successfully developed and applied to epitaxial layers containing high indium mole fraction InGaAs channels grown on GaAs substrates. A unique gate recess process was adopted to significantly increase device gain by effectively suppressing output conductance and feedback capacitance. Coupled with extremely small 10 mum times 25 mum via holes on substrates thinned to 1 mil, we achieved a 13.5 dB maximum stable gain (MSG) at 110 GHz for a 30-mum gate-width device. To our knowledge, this is the highest gain performance reported for microwave high electron-mobility transistor devices of similar gate periphery at this frequency, and equivalent circuit modeling indicates that this device will operate at frequencies beyond 300 GHz.     

Uniform, high-gain AlGaAs/In0.05Ga0.95As/GaAsP-n-p heterojunction bipolar transistors by dual selective etch process

AlGaAs/InGaAs/GaAs P-n-p heterojunction bipolar transistors (HBTs) have been fabricated using a dual selective etch process. In this process, a thin AlGaAs surface passivation layer surrounding the emitter is defined by selective etching of the GaAs cap layer. The InGaAs base is then exposed by selective etching of the AlGaAs emitter. The resulting devices were very uniform, with current gain varying by less than ±10% for a given device size. Current gain at a given emitter current density was independent of device size, with gains of over 200 obtained at current densities above 5×10⁴ A/cm ²     

Effect of a Two-Step Recess Process Using Atomic Layer Etching on the Performance of In0.52Al0.48As/In0.53Ga0.47As p-HEMTs

The characteristics of 0.15- mum InAlAs/InGaAs pseudomorphic high-electron mobility transistors (p-HEMTs) that were fabricated using the Ne-based atomic layer etching (ALET) technology and the Ar-based conventional reactive ion etching (RIE) technology were investigated. As compared with the RIE, the ALET used a much lower plasma energy and thus produced much lower plasma-induced damages to the surface and bulk of the In_0.52AI_0.48As barrier and showed a much higher etch selectivity (~70) of the InP spacer against the In_0.52Al_0.48As barrier. The 0.15-mum InAlAs/InGaAs p-HEMTs that were fabricated using the ALET exhibited improved G_m,max (1.38 S/mm), I_ONn/I_OFF(1.18X10⁴), drain-induced barrier lowering (80 mWV), threshold voltage uniformity (V_th,avg = -190 mV and alpha = 15 mV), and ftau (233 GHz), mainly due to the extremely low plasma-induced damage in the Schottky gate area.     

InP/InGaAs HBTs with n+-InP contacting layers grown byMOMBE using SiBr4

InP/InGaAs heterojunction bipolar transistors (HBTs) with low resistance, nonalloyed TiPtAu contacts on n⁺-InP emitter and collector contacting layers have been demonstrated with excellent DC characteristics. A specific contact resistance of 5.42×10^-8 Ω·cm², which, to the best of our knowledge, is the lowest reported for TiPtAu on n-InP, has been measured on InP doped n=6.0×10¹⁹ cm^-3 using SiBr₄. This low contact resistance makes TiPtAu contacts on n-InP viable for InP/InGaAs HBTs     

In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As abrupt double-heterojunction bipolar transistors

In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As n-p-n abrupt double-heterojunction bipolar transistors grown by molecular beam epitaxy (MBE) have been realized for the first time. DC current gains in excess of 300 have been measured on devices operated in the emitter-up configuration. DC current gains around 50 are obtained on device structures with Be+ implanted extrinsic base regions operated in the emitter-down configuration. The carrier injection and collection behavior of the abrupt InGaAs/InAlAs heterojunctions is discussed.     

Device characterization on monocrystalline silicon grown over SiO2by the ELO (epitaxial lateral overgrowth) process

MOS and lateral bipolar transistors have been fabricated on epitaxial silicon layers which have been laterally overgrown over SiO2. These device characteristics were than compared to those measured on devices fabricated on homoepitaxial silicon and bulk silicon. The measurements indicate essentially identical MOS device characteristics for all three materials with a typical hole field effect mobility of about 180 cm²/vs. Lifetime measurements using pulsed C-V techniques showed essentially the same values for ELO material and homoepitaxial material with the ELO value being about 20 µS for 10¹⁵cm^-3doping level. These lifetime values correlate will with diode and bipolar transistor measurements.     

LP－MOCVD生长InGaAs／GaAs量子阱

用低压ＭＯＣＶＤ（ＬＰ－ＭＯＣＶＤ）生长三种不同的ＩｎＧａＡｓ／ＧａＡｓ应变层量子阱材料，其中两种含ＡｌＧａＡｓ限制层。结果表明，ＡｌＧａＡｓ限制层对量子阱的发光强度影响很大，与没有ＡｌＧａＡｓ限制层的结果相比，带ＡｌＧａＡｓ限制层的结构的发光强度要强一个数量级以上。在低温（１８Ｋ）ＰＬ光谱图中，我们看到，除了存在主峰以外，在主峰两侧还各有一个子峰，这些子峰可能与量子阱的质量有关。     

Spontaneous Radiative Efficiency and Gain Characteristics of Strained-Layer InGaAs–GaAs Quantum-Well Lasers

The optical gain spectra, unamplified spontaneous emission spectra, and spontaneous radiative efficiency are extracted from the measurement of amplified spontaneous emission (ASE) on a single pass, segmented contact 0.98-mum-emitting aluminum-free InGaAs-InGaAsP-GaAs quantum-well (QW) laser diode. These measurements provide a baseline for which to compare higher strain InGaAs QW lasers emitting near 1.2 mum. The peak gain-current relationship is extracted from gain spectra and the peak gain parameter go is found to agree within 25% of the value extracted using conventional cavity length analysis for 0.98-mum-emitting devices. The spontaneous radiative current is extracted using the fundamental connection between gain and unamplified spontaneous emission, which in turn gives an estimate of the amount of nonradiative recombination in this material system. The spontaneous radiative efficiency, the ratio of spontaneous radiative current to total current, at room temperature of 0.98-mum-emitting InGaAs QW laser material is found to be in the range of 40%-54%, which is 2.5-3.5 times larger than that of highly strained InGaAs QW laser emitting near lambda = 1.2 mum. Whereas the gain parameter, g₀ = dg/d(ln j), was measured to be 1130 and 1585 cm^-1 for the 0.98-mum- and 1.2-mum-emitting materials, respectively. From the calculated below threshold current injection efficiency of 75%-85%, we deduce that the internal radiative efficiency of the QW material is ~ 20% higher than the ratio of internal radiative current to external injected current extracted directly from ASE measurements.     

Self-aligned In0.53Ga0.47As/semi-insulating/n+InP junction field-effect transistors

Depletion-mode junction field-effect transistors (JFET's) with InGaAs p-n junctions grown on compensated Fe:InP or highly resistive In0.52Al0.48As isolation layers grown on n⁺-InP substrates have been fabricated using a combination of molecular-beam epitaxy and metalorganic chemical vapor deposition growth techniques. Using a self-aligned gate technology with a 1-µm gate length, devices with high transconductance (80 mS/mm), low leakage current (<100 nA), and a gate-to-source capacitance of 0.4 pF have been fabricated. This is apparently the first report where InP-based alloy FET's have been fabricated on an isolated n⁺-substrate. This structure has application to monolithically integrated photoreceivers.     

Low frequency noise sources in InAlAs/InGaAs MODFETs

Detailed analysis of the 1/f low-frequency noise (LFN) in In/sub 0.52/Al/sub 0.48/As/InGaAs MODFET structures is performed, for low drain bias (below pinch-off voltage), in order to identify the physical origin and the location of the noise sources responsible for drain current fluctuations in the frequency range 0.1 Hz-10/sup 5/ Hz. Experimental data were analyzed with the support of a general modeling of the 1/f LFN induced by traps distributed within the different layers and interfaces which constitute the heterostructures. Comparative noise measurements are performed on a variety of structures with different barrier (InAIAs, InP) and different channel (InGaAs lattice matched to InP, strained InGaAs, InP) materials. It is concluded that the dominant low frequency noise sources of InAlAs/InGaAs MODFET transistors in the ON state are generated by deep traps distributed within the "bulk" InAlAs barrier and buffer layers. For reverse gate bias, the gate current appears to be the dominant contribution to the channel LFN, whereas both the gate current and the drain and source ohmic contacts are the dominant sources of noise when the device is biased strongly in the ON state. Heterojunction FET's on InP substrate with InP barrier and buffer layers show significantly lower LFN and appear to be more suitable for applications such as nonlinear circuits that have noise upconversion.     

High-temperature operation of InGaAs/InGaAsP compressive-strainedQW lasers with low threshold currents

We investigated the influence of the band gap wavelength of barrier layers and separate confinement heterostructure (SCH) layers λ_SCH on the high-temperature operation of InGaAs/InGaAsP compressive-strained quantum-well (QW) lasers. The optimum λ_SCH was 1.2 μm, at which carriers were sufficiently confined into quantum wells. The QW laser with λ_SCH = 1.2 μm exhibited low threshold currents of 2.3 mA at 20°C and 9.7 mA at 100°C and CW lasing up to 150°C     

Enhancement-Mode GaAs MOSFETs With an In0.3 Ga0.7As Channel, a Mobility of Over 5000 cm2/V ·s, and Transconductance of Over 475 μS/μm

We present metal-gate high-k-dielectric enhancement-mode (e-mode) III-V MOSFETs with the highest reported effective mobility and transconductance to date. The devices employ a GaGdO high-k (k = 20) gate stack, a Pt gate, and a delta-doped InGaAs/AlGaAs/GaAs hetero-structure. Typical 1-mum gate length device figures of merit are given as follows: saturation drive current, I_d,sat = 407 muA/mum; threshold voltage, V_t = +0.26 V; maximum extrinsic transconductance, g_m = 477 muS/mum (the highest reported to date for a III-V MOSFET); gate leakage current, I_g = 30 pA; subthreshold swing, S = 102 mV/dec; on resistance, R_on = 1920 Omega-mum; I_on/I_off ratio = 6.3 x 10⁴; and output conductance, g_d = 11 mS/mm. A peak electron mobility of 5230 cm²/V. s was extracted from low-drain-bias measurements of 20 mum long-channel devices, which, to the authors' best knowledge, is the highest mobility extracted from any e-mode MOSFET. These transport and device data are highly encouraging for future high-performance n-channel complementary metal-oxide-semiconductor solutions based on III-V MOSFETs.     

Current reversals in p−n−p transistors

p−n−p silicon bipolar junction transistors (BJTs) have received a greater attention recently in light of the emerging dilemma of performance and power requirements for bipolar VLSI. The current reversal phenomena due to the avalanche breakdown have been the focus of the study of advanced Si p−n−p BJTs in the past. However, a thorough study of current reversals in p−n−p transistors has not been presented yet. In this paper, we study the base and collector current reversals in the inverse mode and their associated physical mechanisms. The collector and base current reversals have been found when the device is operated with or without avalanche effect. Physical mechanisms have been proposed to interpret these phenomena.     

High-performance strain-compensated InGaAs-GaAsP-GaAs(λ=1.17 μm) quantum well diode lasers

This letter reports studies on highly strained and strain-compensated InGaAs quantum-well (QW) active diode lasers on GaAs substrates, fabricated by low-temperature (550°C) metal-organic chemical vapor deposition (MOCVD) growth. Strain compensation of the (compressively strained) InGaAs QW is investigated by using either InGaP (tensile-strained) cladding layer or GaAsP (tensile-strained) barrier layers. High-performance λ=1.165 μm laser emission is achieved from InGaAs-GaAsP strain-compensated QW laser structures, with threshold current densities of 65 A/cm² for 1500-μm-cavity devices and transparency current densities of 50 A/cm². The use of GaAsP-barrier layers are also shown to significantly improve the internal quantum efficiency of the highly strained InGaAs-active laser structure. As a result, external differential quantum efficiencies of 56% are achieved for 500-μm-cavity length diode lasers