InGaP/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor with a liquid-phase-oxidized InGaP as gate dielectric

An InGaP/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor (MOS-PHEMT) with a thin InGaP oxide layer as the gate dielectric is demonstrated. The MOS-PHEMT not only has the advantages of the MOS structure but also has the high-density, high-mobility 2DEG channel. The MOS-PHEMTs have larger gate swing voltages, lower gate leakage currents, and higher breakdown voltages than their counterpart PHEMTs have. Thus, the proposed MOS-PHEMT may be promising in power device applications.     

Control of threshold voltage and improved subthreshold swing in enhancement-mode InGaP/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor

The InGaP/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor (MOS-PHEMT) with an oxidized GaAs gate by liquid phase oxidation (LPO) is demonstrated. With the help of the LPO, the threshold voltage (V_th) can be shifted positively to 0.07 V, and enhancement-mode MOS-PHEMT is fabricated. The device with a gate metal of 1 × 100 μm² shows a maximum transconductance of 171 mS/mm at V_DS = 5 V and a maximum drain current density of 182 mA/mm at V_GS = 2 V. It also exhibits a lower leakage current and an improved subthreshold swing compared to the referenced Schottky-gate InGaP/InGaAs PHEMT.     

增强型InGaP/AlGaAs/InGaAs PHEMT栅退火工艺

针对InGaP/AlGaAs/lnGaAs PHEMT器件,进行了Ti/Pt/Au和Pt/Ti/Pt/Au两种栅金属结构的退火实验,通过实验研究比较,得到了更适用于增强型器件的退火工艺,利用Ti/Pt/Au结构,在320℃退火40min,使器件阈值电压正向移动大约200mV,从而成功制作了高成品率的稳定一致的增强型器件,保证了增强型器件阈值电压在零以上.     

Life‐cycle assessment of photovoltaic modules: Comparison of mc‐Si,InGaP and InGaP/mc‐Si solar modules

A higher conversion efficiency of photovoltaic modules does not automatically imply a lower environmental impact, when the life‐cycle of modules is taken into account. An environmental comparison is carried out between the production and use phase, except maintenance, of an indium–gallium–phosphide (InGaP) on multicrystalline silicon (mc‐Si) tandem module, a thin‐film InGaP cell module and a mc‐Si module. The evaluation of the InGaP systems was made for a very limited industrial production scale. Assuming a fourfold reuse of the GaAs substrates in the production of the thin‐film InGaP (half) modules, the environmental impacts of the tandem module and of the thin‐film InGaP module are estimated to be respectively 50 and 80% higher than the environmental impact of the mc‐Si module. The energy payback times of the tandem module, the thin‐film InGaP module and the mc‐Si module are estimated to be respectively 5.3, 6.3 and 3.5 years. There are several ways to improve the life‐cycle environmental performance of thin‐film InGaP cells, including improved materials efficiency in production and reuse of the GaAs wafer and higher energy efficiency of the metalorganic chemical vapour deposition process. Copyright © 2003 John Wiley & Sons, Ltd.     

Comparison of OMVPE Grown GaAs/AlGaAs and GaAs/InGaP HEMT and PHEMT structures

Symmetric δ-doped InGaP and AlGaAs PHEMT structures have been grown by organometallic vapor phase epitaxy with properties that approach those of MBE grown AlGaAs structures. The 300 and 77K carrier concentrations for the InGaP PHEMT were 2.72 and 2.56 × 10¹² cm^{2 −2} and the mobilities were 5,920 and 22,000 cm^{2 2}/V.s. These excellent values suggest that problems associated with switching the anion at the channel heterojunction have been overcome. The corresponding values for the AlGaAs PHEMT were 2.51 and 2.19 × 10¹² cm^{2 −2} and 6,500 and 20,400 cm²/V.s. The uniformity in the indium concentration in the InGaAs layer as determined by photoluminescence, photoreflection, double crystal x-ray diffraction, and Rutherford backscattering was found to be good, but the percent In in the AlGaAs pseudo-morphic high electron mobility transistor (PHEMT) was less than that in the InGaP PHEMT even though the programmed values were the same. The uniformity in the doping distribution as determined by secondary ion mass spectroscopy and electrochemical capacitance-voltage measurements was found to be good, but it decreased with distance from the center of the susceptor. Also, most of the dopants in the δ-doped InGaP and AlGaAs layers were activated.     

Gate length scaling in high performance InGaP/InGaAs/GaAs pHEMTs

The performance of InGaP-based pHEMTs as a function of gate length has been examined experimentally. The direct-current and microwave performance of pHEMTs with gate lengths ranging from 1.0-0.2 μm has been evaluated. Extrinsic transconductances from 341 mS/mm for 1.0 μm gate lengths to 456 mS/mm for 0.5 μm gate lengths were obtained. High-speed device operation has been verified, with f_t of 93 GHz and f_max of 130 GHz for 0.2 μm gate lengths. The dependence of DC and small-signal device parameters on gate length has been examined, and scaling effects in InGaP-based pHEMT's are examined and compared to those for AlGaAs/InGaAs/GaAs pHEMTs. High-field transport in InGaP/InGaAs heterostructures is found to be similar to that of AlGaAs/InGaAs heterostructures. The lower ϵ_r of InGaP relative to AlGaAs is shown to be responsible for the early onset of short-channel effects in InGaP-based devices     

增强型InGaP/AlGaAs/InGaAs PHEMT小信号等效电路参数的提取

介绍了增强型InGaP/AlGaAs/InGaAs PHEMT小信号等效电路中元件参数值的提取方法,并利用IC-CAP软件EEHEMT1模型提取了参数.利用ADS软件验证了提参结果,ADS仿真的直流I-V曲线和S参数与实测结果基本吻合.结果表明EEHEMT1模型可以用于提取增强型PHEMT参数,并且具有可操作性.     

增强型InGaP/AlGaAs/InGaAs PHEMT小信号等效电路参数的提取

介绍了增强型InGaP／AlGaAs／InGaAs PHEMT小信号等效电路中元件参数值的提取方法，并利用IC-CAP软件EEHEMT1模型提取了参数．利用ADS软件验证了提参结果，ADS仿真的直流I-V曲线和S参数与实测结果基本吻合．结果表明EEHEMT1模型可以用于提取增强型PHEMT参数，并且具有可操作性．     

新结构InGaP/GaAs/InGaP DHBT生长及特性研究

设计并生长了一种新的InGaP/GaAs/InGaP DHBT结构材料,采用在基区和集电区之间插入n+-InGaP插入层结构,以解决InGaP/GaAs/InGaP DHBT集电结导带尖峰的电子阻挡效应问题。采用气态源分子束外延(GSMBE)技术,通过优化生长条件,获得了高质量外延材料,成功地生长出带有n+-InGaP插入层结构的GaAs基InGaP/GaAs/InGaP DHBT结构材料。采用常规的湿法腐蚀工艺,研制出发射极面积为100μm×100μm的新型结构InGaP/GaAs/InGaP DHBT器件。直流特性测试的结果表明,所设计的集电结带有n+-InGaP插入层的InGaP/GaAs/InGaP DHBT器件开启电压约为0.15V,反向击穿电压达到16V,与传统的单异质结InGaP/GaAs HBT相比,反向击穿电压提高了一倍,能够满足低损耗、较高功率器件与电路制作的要求。     

New self-aligned T-gate InGaP/GaAs field-effect transistors grownby LP-MOCVD

This paper reports on self-aligned T-gate InGaP/GaAs FETs using n ⁺/N⁺/δ(P⁺)/n structures. N⁺ -InGaP/δ(P⁺)-InGaP/n-GaAs forms a planar-doped barrier. The inherent ohmic gate of camel-gate FETs together with a highly selective etch between an InGaP and a GaAs layers offers a self-aligned T-shape gate with a reduced effective length. A fabricated device with a reduced gate dimension of 1.5×100 (0.6×100) μm² obtained from 2×100 (1×100) μm² gate metal exhibits an extrinsic transconductance, unity-current gain frequency, and unity-power gain frequency of 78 (80) mS/mm, 9 (19.5), and 28 (30) GHz, respectively     

InGaP/GaAs heterojunction bipolar transistor grown on asemi-insulating InGaP buffer layer

To improve electrical isolation and simplify the heterojunction bipolar transistor (HBT) fabrication process, a semi-insulating InGaP buffer layer has been employed in an InGaP/GaAs HBT. Data is presented that demonstrates this buffer layer serves as an excellent isolation material. In addition, high-frequency HBT's have been fabricated and characterized to show that the buffer layer does not degrade device performance     

Super low noise InGaP gated PHEMT

Very high performance InGaP/InGaAs/GaAs PHEMTs will be demonstrated. The fabricated InGaP gated PHEMTs devices with 0.25 × 160/cm² and 0.25 × 300 μm² of gate dimensions show 304 mA/mm and 330 mA/mm of saturation drain current at V_GS = 0 V, V_DS = 2 V, and 320 mS/mm and 302 mS/mm of extrinsic transconductances, respectively. Noise figures for 160 μm and 300 μm gate-width devices at 12 GHz are measured to be 0.46 dB with a 13 dB associated gain and 0.49 dB with a 12.85 dB associated gain, respectively. With such a high gain and low noise, the drain-to-gate breakdown voltage can be larger than 11 V. Standard deviation in the threshold voltage of 22 mV for 160 μm gate-width devices across a 4-in wafer can be achieved using a highly selective wet recess etching process. Good thermal stability of these InGaP gated PHEMTs is also presented     

Highly doped InGaP/InGaAs/GaAs pseudomorphic HEMT's with 0.35 μmgates

We fabricated 0.35-μm gate-length pseudomorphic HEMT DCFL circuits using a highly doped thin InGaP layer as the electron supply layer. The InGaP/InGaAs/GaAs pseudomorphic HEMT grown by MOVPE is suitable for short gate-length devices with a low supply voltage since it does not show short channel effects even for gate length down to 0.35 μm. We obtained a K value of 555 mS/Vmm and a transconductance g_m of 380 mS/mm for an InGaP layer 18.5 nm thick. Fabricated 51-stage ring oscillators show the basic propagation delay of 11 ps and the power-delay product of 7.3 fJ at supply voltage of V_DD of 1 V, and 13.8 ps and 3.2 fJ at V_DD of 0.6 V for gates 10 μm wide     

Comparative study of InGaP/GaAs high electron mobility transistors with upper and lower delta-doped supplied layers

Influence corresponding to the position of δ-doped supplied layer on InGaP/GaAs high electron mobility transistors is comparatively studied by two-dimensional simulation analysis. The simulated results exhibit that the device with lower δ-doped supplied layer shows a higher gate potential barrier height, a higher saturation output current, a larger magnitude of negative threshold voltage, and broader gate voltage swing, as compared to the device with upper δ-doped supplied layer. Nevertheless, it has smaller transconductance and inferior high-frequency characteristics in the device with lower δ-doped supplied layer. Furthermore, a knee effect in current-voltage curves is observed at low drain-to-source voltage in the two devices, which is investigated in this article.     

Further Suppression of Surface-Recombination of an InGaP/GaAs HBT by Conformal Passivation

Conformal passivation on an InGaP/GaAs HBT with significant reduction in the base surface-recombination effect is demonstrated. Not only dc behaviors but also RF performances are remarkably improved compared with the conventional emitter-ledge structure. Based on the conformal passivation, i.e., the base surface is covered by the depleted InGaP ledge structure and sulfur ((NH₄)₂S_x ) treatment, lower base surface-recombination current density, lower specific contact resistance, lower sheet resistance, higher current gain, higher collector current, and higher maximum oscillation frequency are obtained     

Surface recombination current in InGaP/GaAs heterostructure-emitterbipolar transistors

The behavior of the surface recombination current was examined in InGaP/GaAs heterostructure-emitter bipolar transistors (HEBT's) with both exposed GaAs surface and InGaP passivated surface based on the emitter-size effect on current gain. The results indicate that the GaAs surface recombination current has a 1 kT-like dependence in the high current regime and a 2 kT-like dependence in the low current regime which is similar to published experimental results in AlGaAs/GaAs and InGaP/GaAs HBT's. The surface recombination current in devices with an InGaP passivation layer has an order of magnitude lower value in low current regime and more than two orders lower in high current regime than that in devices with exposed GaAs surface     

Effect of Gate Sinking on the Device Performance of the InGaP/AlGaAs/InGaAs Enhancement-Mode PHEMT

An enhancement-mode InGaP/AlGaAs/InGaAs pseudomorphic high-electron mobility transistor using platinum (Pt) as the Schottky contact metal was investigated for the first time. Following the Pt/Ti/Pt/Au gate metal deposition, the devices were thermally annealed at 325 degC for gate sinking. After the annealing, the device showed a positive threshold voltage (V_th) shift from 0.17 to 0.41 V and a very low drain leakage current from 1.56 to 0.16 muA/mm. These improvements are attributed to the Schottky barrier height increase and the decrease of the gate-to-channel distance as Pt sinks into the InGaP Schottky layer during gate-sinking process. The shift in the V_th was very uniform across a 4-in wafer and was reproducible from wafer to wafer. The device also showed excellent RF power performance after the gate-sinking process     

A novel InGaP/InGaAs/GaAs double /spl delta/-doped pHEMT with camel-like gate structure

The author reports a novel InGaP/InGaAs/GaAs double delta-doped pseudomorphic high-electron mobility transistor (pHEMT) with n/sup +/-GaAs/p/sup +/-InGaP/n-InGaP camel-like gate structure grown by MOCVD. Due to the p-n depletion from the p/sup +/-InGaP gate to the channel region and the presence of /spl Delta/Ec at the InGaP/InGaAs heterostructure, the turn-on voltage of gate is larger than 1.7 V. For a 1/spl times/100-/spl mu/m/sup 2/ device, the experimental results show an extrinsic transconductance of 107 mS/mm and a saturation current density of 850 mA/mm. Significantly, an extremely broad gate voltage swing larger than 6 V with above 80% maximum g/sub m/ is obtained. Furthermore, the unit current cut-off frequency f/sub T/ and maximum oscillation frequency are up to 20 and 32 GHz, respectively. The excellent device performance provides a promise for linear and large signal amplifiers and high-frequency circuit applications.     

Performance dependence of InGaP/InGaAs/GaAs pHEMTs on gatemetallization

The performance of InGaP-based pHEMTs as a function of gate metallization is examined for Mo/Au, Ti/Au, and Pt/Au gates. DC and microwave performance of pHEMT's with 0.7-μm gate lengths is evaluated. Transconductance, threshold voltage, f_t, and f_max are found to depend strongly on gate metallization. High-speed performance is achieved, with f_t of 41.3 GHz and f _max of 101 GHz using Mo/Au gates. The difference in performance between devices with different gate metallizations is postulated to be due to a combination of the difference in Schottky barrier heights and different gate-to-channel spacings due to penetration of the gate metal into the InGaP barrier layer     

Simulated analysis for InGaP/GaAs heterostructure-emitter bipolar transistor with InGaAs/GaAs superlattice-base structure

A novel InGaP/GaAs heterostructure-emitter bipolar transistor (HEBT) with InGaAs/GaAs superlattice-base structure is proposed and demonstrated by two-dimensional analysis. As compared with the traditional HEBT, the studied superlattice-base device exhibits a higher collector current, a higher current gain of 246, and a lower base–emitter (B–E) turn-on voltage of 0.966 V at a current level of 1 μA, attributed to the increased charge storage of minority carriers in the InGaAs/GaAs superlattice-base region by tunneling behavior. The low turn-on voltage can reduce the operating voltage and collector–emitter offset voltage for low power consumption in circuit applications.