Buried-Pt gate InP/In0.52Al0.48As/In0.7Ga0.3As pseudomorphic HEMTs

InP-based high electron mobility transistors (HEMTs) were fabricated by depositing Pt-based multilayer metallization on top of a 6-nm-thick InP etch stop layer and then applying a post-annealing process. The performances of the fabricated 55-nm-gate HEMTs before and after the post-annealing were characterized and were compared to investigate the effect of the penetration of Pt through the very thin InP etch stop layer. After annealing at 250 °C for 5 min, the extrinsic transconductance (G_m) was increased from 1.05 to 1.17 S/mm and Schottky barrier height was increased from 0.63 to 0.66 eV. The unity current gain cutoff frequency (f_T) was increased from 351 to 408 GHz, and the maximum oscillation frequency (f_max) was increased from 225 to 260 GHz. These performance improvements can be attributed to penetration of the Pt through the 6-nm thick InP layer, and making contact on the InAlAs layer. The STEM image of the annealed device clearly shows that the Pt atoms contacted the InAlAs layer after penetrating through the InP layer.     

Backgating in pseudomorphic In0.15Ga0.85As/Al0.25Ga0.75As MODFET's with a GaAs:Er buffer layer

A new GaAs:Er buffer layer grown by MBE has been developed which significantly reduces backgating currents (by 3 to 4 orders of magnitude) in pseudomorphic InGaAs/AlGaAs modulation-doped field effect transistors (MODFET's). The buffer layer is highly resistive, in the 10 ²-10⁵ Ω·cm range over the Er-doping range investigated. Presence of internal Schottky barriers resulting from high-density ErAs precipitates has been proposed to he the cause of the high resistivity     

Electron transport in 0.15-μm gate In0.52Al0.48As/In0.53Ga0.47As HEMT

Magneto-transport and cyclotron resonance measurements were made to determine directly the density, mobility, and the effective mass of the charge carriers in a high-performance 0.15-μm gate In_0.52 Al_0.48As/In_0.53Ga_0.47As high-electron-mobility transistor (HEMT) at low temperatures. At the gate voltage V_G=0 V, the carrier density n _g under the gate is 9×10¹¹ cm^-2, while outside of the gate region n_g=2.1×10¹² cm^-2. The mobility under the gate at 4.2 K is as low as 400 cm²/V-s when V_G<0.1 V and rapidly approaches 11000 cm²/V-s when V_G>0.1 V. The existence of this high mobility threshold is crucial to the operation of the device and sets its high-performance region in V_G>0.1 V     

Tunneling between two quantum wells: In0.53Ga0.47As/InP versus GaAs/Al0.35Ga0.65As

The electron transfer from a narrow to a wide quantum well through a thin barrier is studied in the non-resonant case by time-resolved photoluminescence. The two systems In_0.53Ga_0.47As/InP and GaAs/Al_0.35Ga_0.65As are compared. Space charge effects are investigated and discussed. Contributions of holes to the tunneling process are determined.     

Thermal stability of MISFET with low-temp molecular-beamepitaxy-grown GaAs and Al0.3Ga0.7As gate ins

GaAs and Al_0.3Ga_0.7As epilayers grown at LT by MBE were used as insulators in the fabrication of MISFET devices. Parametric changes were used to evaluate the thermal stability of MISFET, to identify failure mechanisms and validate the reliability of these devices. The LT-Al_0.3Ga_0.7As MISFET showed superior thermal stability. The degradation in the performance of MISFET with 1000 Å thick LT-GaAs gate insulator was worse than those of the MESFET. On the other hand, MISFET with 250 Å thick LT-GaAs gate insulators exhibited stable characteristics with thermal stressing, LF (low frequency) noise studies on the TLM structures of MISFET layers exhibited 1/f noise in the LT-Al_0.3Ga_0.7As samples and 250 Å LT-GaAs samples; whereas the 1000 Å thick LT-GaAs samples exhibited 1/f^3/2 noise, which was attributed to: (i) the thermal noise generated at the interface of the insulator, and (ii) the active layer due to the outdiffused metallic arsenic. Reverse gate-drain current degradation experiments were carried out at 120°C, 160°C, 200°C, and 240°C. Transconductance frequency dispersion studies were carried out before and after thermal stress on these MISFET. The transconductance of MISFET with 1000 Å LT-GaAs gate insulators was degraded by 40% at 100 kHz after thermal stress. The rest of the samples exhibited stable characteristics. These results indicate that composition changes had occurred at the interface in thicker LT-GaAs MISFET structures. Thinner LT-layers are ideal for achieving higher transconductance and better thermal stability without sacrificing the power capability of MISFET     

22 nm In0.75Ga0.25As channel-based HEMTs on InP/GaAs substrates for future THz applications

In this work, the performance of L_g=22 nm In_0.75Ga_0.25As channel-based high electron mobility transistor (HEMT) on InP substrate is compared with metamorphic high electron mobility transistor (MHEMT) on GaAs substrate. The devices features heavily doped In_0.6Ga_0.4As source/drain (S/D) regions, Si double δ-doping planar sheets on either side of the In_0.75Ga_0.25As channel layer to enhance the transconductance, and buried Pt metal gate technology for reducing short channel effects. The TCAD simulation results show that the InP HEMT performance is superior to GaAs MHEMT in terms of f_T, f_max and transconductance (g_{m_max}). The 22 nm InP HEMT shows an f_T of 733 GHz and an f_max of 1340 GHz where as in GaAs MHEMT it is 644 GHz and 924 GHz, respectively. InGaAs channel-based HEMTs on InP/GaAs substrates are suitable for future sub-millimeter and millimeter wave applications.     

Quantum-well Hall devices in Si-delta-dopedAl0.25Ga0.75As/GaAs and pseudomorphic Al0.25Ga0.75As/In0.25Ga0.75As/GaAsheterostructures grown by LP-MOCVD: performance comparisons

Characterized herein are quantum-well Hall devices in Si-delta-doped Al_0.25Ga_0.75As/GaAs and pseudomorphic Al_0.25Ga_0.75As/In_0.25Ga _0.75As/GaAs heterostructures, grown by low-pressure metal organic chemical vapor deposition method. The Si-delta-doping technique has been applied to quantum-well Hall devices for the first time. As a result high electron mobilities of 8100 cm^-2/V·s with a sheet electron density of 1.5×10¹² cm^-2 in Al_0.25Ga_0.75As/In_0.25Ga_0.75 As/GaAs structure and of 6000 cm^-2/V·s with the sheet electron density of 1.2×10¹² cm^-2 in Al_0.25Ga_0.75As/GaAs structure have been achieved at room temperature, respectively. From Hall devices in Al_0.25Ga_0.75As/In_0.25Ga_0.75 As structure, the product sensitivity of 420 V/AT with temperature coefficient of -0.015 %/K has been obtained. This temperature characteristic is one of the best result reported. Additionally, a high signal-to-noise ratio corresponding to the minimum detectable magnetic field of 45 nT at 1 kHz and 75 nT at 100 Hz has been attained. These resolutions are among the best reported results     

Impedance, modulation response, and equivalent circuit ofultra-high-speed In0.35Ga0.65As/GaAs MQW laserswith p-doping

On-wafer measurements of the frequency-dependent impedance, modulation response, and RIN power spectra of ultra-high-speed p-doped In_0.35Ga_0.65As/GaAs MQW lasers are presented and analyzed. The experimental results are shown to be accurately modeled by an equivalent circuit which accounts for both the carrier transport/capture dynamics and the junction space-charge capacitance. We find that the carrier escape time out of the QW's in our laser structure is much larger. Than the carrier capture time, and therefore the interplay between carrier capture and re-emission is not affecting the high-speed modulation dynamics. On the other hand, the absolute values of both the carrier capture time and the space-charge capacitance still limit the modulation bandwidth     

Fabrication of 80-nm T-gate high indium In0.7Ga0.3As/In0.6Ga0.4As composite channels mHEMT on GaAs substrate with simple technological process

An 80-nm gate length metamorphic high electron mobility transistor (mHEMT) on a GaAs substrate with high indium composite compound-channels In_0.7Ga_0.3As/In_0.6Ga_0.4As and an optimized grade buffer scheme is presented. High 2-DEG Hall mobility values of 10200 cm²/(V· s) and a sheet density of 3.5 × 10¹² cm^-2 at 300 K have been achieved. The device's T-shaped gate was made by utilizing a simple three layers electron beam resist, instead of employing a passivation layer for the T-share gate, which is beneficial to decreasing parasitic capacitance and parasitic resistance of the gate and simplifying the device manufacturing process. The ohmic contact resistance R_c is 0.2 Ω ·mm when using the same metal system with the gate (Pt/Ti/Pt/Au), which reduces the manufacturing cycle of the device. The mHEMT device demonstrates excellent DC and RF characteristics. The peak extrinsic transconductance of 1.1 S/mm and the maximum drain current density of 0.86 A/mm are obtained. The unity current gain cut-off frequency (f_T) and the maximum oscillation frequency (f_max) are 246 and 301 GHz, respectively.     

88 nm栅长fmax＝201 GHz InP基In0.53Ga0.47As/In0.52Al0.48As HEMT器件

我们成功研制了栅长88 nm, 栅宽2 50 μm, 源漏间距为2.4 μm 的InP基In0.53Ga0.47As/In0.52Al0.48As高电子迁移率器件(HEMT)。栅是使用PMMA/Al/UVⅢ,通过优化电子束曝光时间及其显影时间的方式制作的。这些器件有比较好的直流及其射频特性：峰值跨导、最大源漏饱和电流密度、开启电压、ft和fmax 分别为765 mS/mm, 591 mA/mm, -0.5 V, 150 GHz 和201 GHz。这些器件将非常适合于毫米波段集成电路。     

DC and microwave performance of a 0.1 μm gate InAs/In0.52Al0.8As MODFET

The authors have measured and analyzed the performance characteristics of 0.1-μm gate InAs/In_0.52Al_0.48 MODFETs grown by molecular beam epitaxy. The transistors are characterized by measured g_m(max)=840 mS/mm, f_T=128 GHz, and a very high current carrying capability, e.g. I_dss=934 mA/mm at V _gs=0.4 V and V_ds=2.7 V. The value of f _T is estimated from extrapolation of the current gain (H ₂₁) at a -6 dB/octave rolloff. This is the first report on the microwave characteristics of an InAs-channel MODFET and establishes the superiority of this heterostructure system     

Transferring of GaAs microtips using selective wet etching Al0.7Ga0.3As sacrificial layer

GaAs pyramidal microtips were successfully transferred from GaAs substrate to target wafer by a simple technique, i.e., selective wet etching off AlGaAs sacrificial layer. A GaAs/Al_0.7Ga_0.3As/GaAs sandwich structure is firstly formed on GaAs (0 0 1) substrate by metalorganic chemical vapor deposition, and then GaAs pyramidal microtips are grown on the sandwich structure using selective liquid-phase epitaxy. The GaAs microtips are removed from the sandwich structure by selective wet etching Al_0.7Ga_0.3As layer using concentrated HCl solution. Finally, the tips are glued onto the target wafer by a negative photoresist. During this transfer process the tips are completely encapsulated in a positive photoresist to protect against attack. Scanning electron microscopy images show that GaAs tips can be successfully transferred without any damage by this technique. The achievement reported here represents a significant step towards the application of scanning near-field optical microscopy.     

Fabrication of 0.15-μm Γ-Shaped Gate In0.52Al0.48As/In0.6Ga0.4As Metamorphic HEMTs Using DUV Lithography and Tilt Dry-Etching Technique

An In_0.52Al_0.48As/In_0.6Ga_0.4 As metamorphic high-electron mobility transistor (MHEMT) with 0.15-mum Gamma-shaped gate using deep ultraviolet lithography and tilt dry-etching technique is demonstrated. The developed submicrometer gate technology is simple and of low cost as compared to the conventional E-beam lithography or other hybrid techniques. The gate length is controllable by adjusting the tilt angle during the dry-etching process. The fabricated 0.15-mum In_0.52Al_0.48As/In_0.6Ga_0.4As MHEMT using this novel technique shows a saturated drain-source current of 680 mA/mm and a transconductance of 728 mS/mm. The f_T and f_max of the MHEMT are 130 and 180 GHz, respectively. The developed technique is a promising low-cost alternative to the conventional submicrometer E-beam gate technology used for the fabrication for GaAs MHEMTs and monolithic microwave integrated circuits     

Characteristics of submicron gate GaAs FET's with Al0.3Ga0.7As buffers: Effects of interface quality

GaAs field effect transistors (FET's) having submicron gate lengths (0.7 µm) and Al0.3Ga0.7As buffer layers were fabricated. The saturation, and particularly the pinch-off characteristics, showed a considerable dependence on the growth conditions used during preparation by molecular beam epitaxy (MBE). The structures grown at high substrate temperatures exhibited an excellent pinch-off characteristic, while those grown at low temperatures showed an inferior pinch-off characteristic. A transconductance of 160 mS/mm was obtained in all structures, regardless of the growth temperature.     

Al0.3Ga0.22In0.48P/GaAs HBT高温特性的研究

本文研制了Al     

Comparison of In0.5Ga0.5P/GaAs single- anddouble-heterojunction bipolar transistors with a carbon-doped base

A comparison of MOCVD-grown, n-p-n In_0.5Ga_0.5P/GaAs single- and double-heterojunction bipolar transistors (SHBTs and DHBTs) with a carbon-doped base is presented. A base doping level of 2.5×10¹⁹ cm^-3 was employed in both device structures, resulting in a base sheet resistance of 500 Ω/sq. Common-emitter current gains as high as 210 and 150 were measured for the SHBTs and DHBTs, respectively. Results of a DC performance optimization study indicate that a 15- and 25-Å undoped set-back layer at the emitter-base junction provides optimal common-emitter current gain. The DHBTs exhibited a 40% improvement in common-base breakdown voltage compared to SHBTs (25 versus 18 V), indicating that In_0.5Ga_0.5P/GaAs DHBTs may prove suitable for power device applications     

Comparison of interfacial and electrical properties between Al2O3 and ZnO as interface passivation layer of GaAs MOS device with HfTiO gate dielectric

GaAs metal–oxide–semiconductor(MOS) capacitors with HfTiO as the gate dielectric and Al2O3 or ZnO as the interface passivation layer(IPL) are fabricated. X-ray photoelectron spectroscopy reveals that the Al2O3 IPL is more effective in suppressing the formation of native oxides and As diffusion than the ZnO IPL. Consequently, experimental results show that the device with Al2O3 IPL exhibits better interfacial and electrical properties than the device with ZnO IPL: lower interface-state density(7.21012 eV1cm2/, lower leakage current density(3.60107A/cm2 at Vg D1 V) and good C–V behavior.     

fT=260 GHz and fmax=607 GHz of 100-nm-gate In0.52Al0.48As/In0.7Ga0.3As HEMTs with Gm.max=1441 mS/mm

The 100-nm T-gate InP-based InAlAs/InGaAs high electron mobility transistors (HEMTs) with the width of 2×50 μm and source-drain space of 2.4 μm are systematically investigated. High indium (In) composition of InGaAs layer was adopted to acquire the higher mobility of the channel layer. A sandwich structure was adopted to optimize the cap layers and produce a very low contact resistance. The fabricated devices exhibit extrinsic maximum transconductance G_m.max=1441 mS/mm, cutoff frequency f_T=260 GHz, and maximum oscillation frequency f_max=607 GHz. A semi-empirical model has been developed to precisely fit the low-frequency region of scattering parameters (S parameters) for InP-based HEMTs. Excellent agreement between measured and simulated S parameters demonstrates the validity of this approach.     

Comparison of the Features of Electron Transport and Subterahertz Generation in Diodes Based on 6-, 18-, 70-, and 120-Period GaAs/AlAs Superlattices

Semiconductors - A comparison of the features of electron transport in diodes based on 6-, 18-, 30-, 70-, and 120-period GaAs/AlAs superlattices with a similar design is performed. However, the...     

Al2O3 stacks on In0.53Ga0.47As substrates: In situ investigation of the interface

In this work we present an in situ investigation of the interface composition between an In_0.53Ga_0.47As substrate and an Al₂O₃ oxide grown by molecular beam deposition in ultra high vacuum conditions. In the effort to improve the chemical quality of the interface, reduction of semiconductor-oxygen bonding at the interface can be obtained by growing a few Å thick pure Al layer before starting exposure of the surface to the atomic oxygen flux. Conversely, when a Ge interface passivation layer is intercalated between the semiconductor and the oxide stack, the interface chemistry is governed by Ge reaction with other species (Al, O), leading only to a partial suppression of the interface oxides.