电流增益截止频率为441 GHz的InGaAs/InAlAs InP HEMT

本文设计并制作了f_T > 400 GHz的In_0.53Ga_0.47As/In_0.52Al_0.48As 铟磷高电子迁移率晶体管（InP HEMT）。采用窄栅槽技术优化了寄生电阻。器件栅长为54.4 nm,栅宽为2 × 50 μm。最大漏极电流I_DS.max为957 mA/mm,最大跨导g_m.max为1265 mS/mm。即使在相对较小的V_DS = 0.7 V下,电流增益截止频率f_T达到了441 GHz,最大振荡频率f_max达到了299 GHz。该器件可应用于太赫兹单片集成放大器和其他电路中。     

调制掺杂对AlGaN/GaN HEMT材料电学性能的影响

利用范德堡Hall方法和汞探针C-V方法,研究了不同Si调制掺杂浓度对AlGaN/GaN HEMT材料电学性质的影响.发现si掺杂可以改善材料电学性能,二维电子气(2DEG)面密度和方块电阻(ns×μ)可以通过si调制掺杂精确控制.当Si掺杂浓度为3×10(18)cm-3时,得到了最低的方块电阻360Ω/□.尽管受到高浓度电子和离化杂质对二维电子气的散射影响,迁移率仍可达1220cm2/(V·s).分析了范德堡Hall方法和汞探针C-V方法的差别,同时测得材料的阈值电压也在合理范围.     

基于低温In_xGa_(1-x)P组分渐变缓冲层的InP/GaAs异质外延

采用低温GaAs与低温组分渐变InxGa1-xP作为缓冲层,利用低压金属有机化学气相外延(LP-MOCVD)技术,在GaAs(001)衬底上进行了InP/GaAs异质外延实验。实验中,InxGa1-xP缓冲层选用组分线性渐变生长模式(xIn0.49→1)。通过对InP/GaAs异质外延样品进行双晶X射线衍射(DCXRD)测试,并比较1.2μm厚InP外延层(004)晶面ω扫描及ω-2θ扫描的半高全宽(FWHM),确定了InxGa1-xP组分渐变缓冲层的最佳生长温度为450℃、渐变时间为500s。由透射电子显微镜(TEM)测试可知,InxGa1-xP组分渐变缓冲层的生长厚度约为250nm。在最佳生长条件下的InP/GaAs外延层中插入生长厚度为48nm的In0.53Ga0.47As,并对所得样品进行了室温光致发光(PL)谱测试,测试结果表明,中心波长为1643nm,FWHM为60meV。     

阴极缓冲层对m-MTDATA/BAlq有机紫外光探测器性能的影响

制备了有机紫外光探测器(OUV-PD),器件结构为I TO/m-MTDATA(30nm)/m-MTDATA:BAlq(40～60nm,1∶1)/BAlq(40nm)/LiF(1nm)/Al(100nm),并研究了施加Liq、TPBi、Bphen和Zn(4-MeBTZ)₂为阴极缓冲层时对器件性 能的影响。实验结果表明,OUV-PD光响应与阴极缓冲层厚度和电子传输性能紧密相关,在 1.05mW/cm²的波长为365nm UV光照射下,响应度最大值分别达到218mA/W、247mA/W、305mA/W 和283mA/W。     

Numerical analysis of device performance of metamorphic InyAl1-yAs/InxGa1-xAs(0.3⩽x⩽0.6) HEMTs on GaAs substrate

A numerical model describing the influence of InAs mole fraction on metamorphic HEMT structures (MM-HEMT) is proposed. The material properties are calculated using the Monte Carlo method, while the charge control law is calculated using a self-consistent solution of Poisson's and Schrodinger's equations. The modeling of the dc, ac, noise and high frequency performance of a device with 0.25-μm gate length is performed using the quasi-two-dimensional (Q2D) approach. This analysis shows that an InAs mole fraction of about 0.40 is an optimum composition for manufacturing high gain, low noise amplifiers. In this range of composition, the performance of MM-HEMT structures is similar to that obtained for lattice-matched HEMTs on InP substrates     

Strained layer InxGa1-xAs/GaAs and InxGa1-xAs/InyGa1-yPmultiple-quantum-well optical modulators grown by gas-source MBE

The first results on low-power p-i-n diode modulator structures using strained multiple quantum wells (MQW's) of InGaAs/InGaP grown by gas-source molecular beam epitaxy (MBE) on GaAs are presented. A comparison of transmission, reflection, and photocurrent spectra for these nonresonant devices with those fabricated from InGaAs/GaAs indicates larger modulation, with a maximum change in reflection of >42% observed at 5-V bias at a wavelength of 0.96 μm     

Fabrication of high-performance AlxGa1-xAs/InyGa1-yAs/GaAs resonant tunneling diodes using amicrowave-compatible technology

A microwave-compatible process for fabricating planar integrated resonant tunneling diodes (RTDs) is described. High-performance RTDs have been fabricated using Al_xGa_1-xAs/In_y Ga_1-yAs/GaAs strained layers. Peak-to-valley current ratios (PVRs) of 4.8:1 with simultaneous peak current densities of 4×10⁴ A/cm² have been achieved at room temperature for diodes of area 9 μm². Accurate measurements of reflection gain versus frequency between 1.5 and 26.5 GHz in the negative differential region indicate that the present technology is promising for millimeter-wave integrated circuits including self-oscillating mixers, frequency multipliers, and detectors     

Short pulse transfer characteristics of AlxGa1-xAs/GaAs andAlxGa1-xAs/InyGa1-yAsmodulation-doped heterojunction FET's

Short-pulse drain current versus gate voltage transfer characteristics measured for modulation-doped HFETs (MODFETs) with four donor-layer-channel-layer combinations-(1) Al_0.3Ga_0.7 As-GaAs, (2) Al_0.2Ga_0.8As-GaAs, (3) Al_0.3Ga_0.7As-In_0.2Ga_0.8As, and (4) Al_0.2Ga_0.8As-In_0.2 a_0.8 As-are compared with the DC transfer characteristics. The measurements are relevant to high-speed switching in HFET circuits. Significant shifts in threshold voltage are observed between the DC and short-pulse characteristics for the structures with n⁺-Al_0.3Ga_0.7As donor layers, while the corresponding shifts for structures with n⁺-Al_0.2Ga_0.8As donor layers are relatively small or virtually nonexistent     

Modeling of short-pulse threshold voltage shifts due to DX centersin AlxGa1-xAs/GaAs and AlxGa1-xAs/InyGa1-yAs MODFET's

The DX-center-related short-pulse threshold voltage shifts (SPTVS) in Al_xGa_1-xAs-based MODFETs is modeled using CBAND, a simulator that solves Poisson equations self-consistently with Schrodinger equations and donor statistics. Using values given in the literature for the DX energy level in Al_xGa_1-xAs this technique gives good agreement between measured and simulated SPTVS for Al_0.3Ga_0.7As/GaAs and Al_0.3Ga_0.7As/In_0.2Ga_0.8As MODFETs. Both simulation and experiment show that the use of Al_0.2 Ga_0.8As in the donor layer reduces the SPTVS relative to the structures using Al_0.3Ga_0.7As. However, the measured shifts at this composition are considerably lower than the simulated values, indicating a DX energy level that may be higher than the value extrapolated from the literature, possibly due to the existence of multiple trap levels. Despite this discrepancy, these results support the use of strained-channel layers and lower Al_x Ga_1-xAs compositions in MODFETs for digital and other large-signal applications requiring good threshold stability     

GaAsxSb1-x/InyAl1-yAsp-channel heterostructure FETs with high transconductance and low gateleakage current

The first known p-channel GaAs_xSb_1-x/In_yAl_1-yAs HFETs on InP are reported. The devices, using a strained-layer GaAs_xSb_1-x channel, have achieved extrinsic transconductances of 40 mS/mm and intrinsic transconductances of 100 mS/mm. In addition to high transconductance, the devices exhibit excellent pinchoff and demonstrate a record gate turn-on voltage of -3 V as a result of extremely low gate leakage currents, making them exceptional candidates for complementary technologies. These outstanding gate characteristics are attributed to the valence band-edge discontinuity of 0.64 eV     

In0.52Al0.48As/InAs/InxAl1-xAs pseudomorphic HEMT's on InP

The DC and microwave performance of an InAs channel HEMT is reported. Room-temperature electron mobility as high as 20200 cm² /Vs is measured, with a high carrier concentration of 2.7×10 ¹² cm^-2. DC extrinsic transconductance of 714 mS/mm is measured and a unity-current-gain cut-off frequency of 50 GHz is obtained for a 1.1-μm gate length HEMT. The success of achieving superior Hall mobility and device performance is strongly dependent on the In_xAl_1-xAs buffer layer design that changes the lattice constant from lattice-matched In_0.52Al_0.48 As to In_0.75Al_0.25As. The multiple In_0.52Al_0.48As/InAs monolayer superlattices buffer achieves the best performance as compared to the step-graded In_x Al_1-xAs and the uniform In_0.76Al_0.25 As buffer     

闪锌矿BxAl1-xAs合金的LP-MOCVD生长研究

利用低压金属有机化学气相沉积(LP-MOCVD)生长工艺,采用三乙基硼(TEB)源,在GaAs(001)衬底上生长了B并入比为0.4%～4.4%的一系列BxAl1-xAs合金。实验结果表明,BxAl1-xAs的最优生长温度为580℃;当生长温度为550℃和610℃时,BxAl1-xAs中B并入比都会下降,550℃时B并入比下降更为显著。在580℃最优生长温度下,B并入比随着TEB摩尔流量增加而提高,且B并入比从临界值2.1%增加至最大值4.4%时,DCXRDω-2θ扫描BxAl1-xAs衍射峰的半高宽值从51.8 arcsec升高到204.7 arcsec,原子力显微镜(AFM)测试表面粗糙度从2.469 nm增大到29.086 nm,说明B并入比超过临界值后BxAl1-xAs晶体质量已经逐渐严重恶化。     

Novel In0.52Al0.48As/In0.53Ga0.47As metamorphic high electron mobility transistors on GaAs substrate with InxGa1−xP graded buffer layers

Compositionally graded In_xGa_1−xP (x=0.48→x=1) metamorphic layers have been grown on GaAs substrate by solid source molecular beam epitaxy using a valved phosphorus cracker cell. Three series of samples were grown to optimize the growth temperature, V/III ratio and grading rate of the buffer layer. X-ray diffraction (XRD) and photoluminescence (PL) were used to characterize the samples. The following results have been obtained: (1) XRD measurement shows that all the samples are nearly fully strain relaxed and the strain relaxation ratio is about 96%; (2) the full-width at half-maximum (FWHM) of the XRD peak shows that the sample grown at 480°C offers better material quality; (3) the grading rate does not influence the FWHM of XRD and PL results; (4) adjustment of the V/III ratio from 10 to 20 improves the FWHM of XRD peak, and the linewidth of PL peak is close to the data obtained for the lattice-matched sample on InP substrate. The optimization of growth conditions will benefit the metamorphic HEMTs grown on GaAs using graded InGaP as buffer layers.     

Impact of surface layer on In0.52Al0.48As/In0.53Ga0.47As/InP high electron mobilitytransistors

The surface potential of FETs has shown a strong effect on the channel potential and charge control in the channel. A study of the role of undoped versus doped cap layers in In_0.52Al_0.48As-In_0.53Ga_0.47 As-InP high-electron-mobility transistors (HEMT) is discussed. As the result of surface potential effect, direct comparison of 0.3×150-μm² gate devices yielded improved gate breakdown characteristics and a DC output conductance of less than 15 mS/mm for the surface undoped structure compared to 50 mS/mm for the doped structure. The surface undoped MEMT achieved a very high maximum stable gain of 19.2 dB compared to 16.0 dB for the surface doped HEMT at 18 GHz, largely due to the improved g_m/g ₀ ratio. This study demonstrates that control of the surface potential in In_0.52Al_0.48As-In_0.53Ga _0.47As-InP HEMTs is consistent with the effect of a gate recess in MESFETs. This study also shows that, in achieving high-gain applications of HEMTs, the surface potential near the gate edge should be optimized through unconventional surface layer design