High thermal stability AlGaAs/InGaAs enhancement-mode pHEMT using palladium-gate technology

The dc, flicker noise, power, and temperature dependence of AlGaAs/InGaAs enhancement-mode pseudomorphic high electron mobility transistors (E-pHEMTs) were investigated using palladium (Pd)-gate technology. Although the conventional platinum (Pt)-buried gate has a high metal work function, which is beneficial for increasing the Schottky barrier height of the E-pHEMT, the high rate of intermixing of the Pt-GaAs interface owing to the effect of the continuous production of PtAs₂ on the device influenced the threshold voltage (V_th) and transconductance (g_m) at high temperatures or over the long-term operation. Variations in these parameters make Pt-gate E-pHEMT-related circuits impractical. Furthermore, a PtAs₂ interlayer caused a serious gate leakage current and unstable Schottky barrier height. This study presents the Pd-GaAs Schottky contact because Pd, an inert material with high work function of 5.12 eV. Stable Pd inhibited the less diffusion at high temperatures and simultaneously suppressed device flicker noise. The V_th of Pd/Ti/Au Schottky gate E-pHEMT was 0.183 V and this value shifted to 0.296 V after annealing at 200 °C. However, the V_th shifted from 0.084 to 0.231 V after annealing of the Pt/Ti/Au Schottky gate E-pHEMT because the Pt sunk into a deeper channel. The slope of the curve of power gain cutoff frequency (f_max) as a function of temperature was −5.76 × 10⁻² GHz/°C for a Pd/Ti/Au-gate E-pHEMT; it was −9.17 × 10⁻² GHz/°C for a Pt/Ti/Au-gate E-pHEMT. The slight variation in the dc and radio-frequency characteristics of the Pd/Ti/Au-gate E-pHEMT at temperatures from 0 to 100 °C revealed that the Pd-GaAs interface has great potential for high power transistors.     

Simulation and Design of AlGaAs/InGaAs CCDs Based on pHEMT Technology

This paper describes the modeling, design, and fabrication of quarter-micrometer double delta-doped AlGaAs/InGaAs charge-coupled devices (CCDs) whose epitaxial layers and geometry were based around the device structure of commercial pHEMTs. A quasi-2-D physical model has been developed to investigate the properties of this novel 2-D electron gas CCD. This physical model allows the characteristics of the InGaAs transport channel as well as the dc characteristics of the device to be predicted within a reasonable amount of time. This model also shows how "individual" charge packets can be controllably transferred through the device when appropriate clocking voltages are applied to the gates of the CCD. This capacitive gate structure device is then shown to be successfully fabricated using established GaAs heterostructure fabrication techniques to ensure good repeatability. The dc characteristics of the fabricated CCD delay line are included.     

Current-voltage behavior of AlGaAs/InGaAs pHEMT structures and the effect of optical illumination

Various pseudomorphic High Electron Mobility Transistor (pHEMT) structures of AlGaAs/InGaAs alloys have been observed their current-voltage behavior. The tungsten probes were used for a measurement the structures by ramping the voltage from −5 to 5 V and measure the electrical current. Measurement was carried out at room temperature and also under optical illumination. From the measurement, the electrical current was found to increase as the increase of Al content in the AlGaAs alloys layer in the pHEMT structure. This phenomenon was supported by the decrease of sheet resistance as obtained from Hall effect measurement. Under visible light illumination, the current-voltage behavior of pHEMT structure was observed to vary as the light power density was varied for 0, 25 and 55 μW/cm.     

Analysis of high power microwave induced degradation and damage effects in AlGaAs/InGaAs pHEMTs

The high power microwave (HPM) induced effects in AlGaAs/InGaAs pseudomorphic high electron mobility transistors (pHEMTs) are investigated by simulation and experiments. Simulated results suggest that the HPM damage mechanism is device burnout, which is caused by emerging current path and strong electric field intensity beneath the gate metal. Besides, analysis points out that the gate metal diffusion may be thermally activated, resulting in DC and RF performance degradation. Specifically, a positive shift will occur to the pinch-off voltage while accordingly the small-signal gain will decrease. The HPM injection experiments on the dual-stage pHEMT low noise amplifiers (LNAs) are carried out. Experimental results substantiate that deterioration happens both in the noise figure and in the small-signal gain, which is in agreement with the simulated results. Failure analysis indicates that the HPM induced failure of LNA is attributed to the failure of the first stage pHEMT. Finally, samples dissection analysis using the scanning electron microscopy (SEM) verifies the simulation analysis of the damage mechanism and the location susceptible to burnout. Meanwhile, the assumption of gate metal diffusion is validated by the observation of pits after removing the gate metal. The performance parameters deterioration can be utilized as the degradation (or damage) criteria, and the mechanisms analysis facilitates making reinforcing design.     

Self-Consistent Simulation of GaAs/InGaAs/AlGaAs Heterostructures Photoluminescence Spectra and Its Application to pHEMT Structures Diagnostics

We performed numerical self-consistent solution of Schrödinger and Poisson equations for GaAs/InGaAs/AlGaAs pHEMT structures with quantum well. Based on the results we calculated optical transition matrix elements and photoluminescence spectra of such structures with the same design and different parameters (such as doping level and epitaxial layers width). In the photoluminescence spectra calculations three fitting parameters have been used. These parameters are GaAs/InGaAs valence band offset in strained quantum well, hole quasi Fermi level and inhomogeneous broadening. The PL peaks amplitudes and positions dependencies on the structure parameters were established. These dependencies can be used as the basis for pHEMT structure non-destructive diagnostics.     

Low degradation rate in strained InGaAs/AlGaAs single quantum welllasers

A 10000 h, 30°C constant-current lifetest performed on five strained In_0.2Ga_0.8As/AlGaAs single-quantum-well lasers, with λ~930 nm, is discussed. The devices are 90-μm×400-μm oxide-stripe lasers with facet coatings, grown by atmospheric pressure organometallic vapor-phase epitaxy. For each diode, the current was maintained at a constant value of ~300 mA, corresponding to approximately 100 mW of output power. After 10⁴ h, thresholds increased from an average of 84 mA to 108 mA, while quantum efficiencies were essentially unchanged. In relation to a typical 100-mW constant-power lifetest, this is equivalent to a degradation rate of less than 1%/kh     

GaAs/AlGaAs and InGaAs/AlGaAs MODFET inverter simulations

Although MODFET's have exhibited the fastest switching speed for any digital circuit technology, there is as yet no clear consensus on optimal inverter design rules. We therefore have developed a comprehensive MODFET device model that accurately accounts for such high gate bias effects as transconductance degradation and increased gate capacitance. The device model, which agrees with experimental devices fabricated in this laboratory, is used in the simulation of direct-coupled FET logic (DCFL) inverters with saturated resistor loads. Based on simulation results, the importance of large driver threshold voltage not only for small propagation delay times but for wide logic swings and noise margins is demonstrated. Furthermore, minimum delay times are found to occur at small supply voltages as seen experimentally. Both of these results are attributed to the reduction of detrimental high gate bias effects. The major effect of reducing the gate length on delay time is to decrease the load capacitance of the gate. Using 0.25-µm gates, delay times of 5 and 3.6 ps at 300 and 77 K, respectively, are predicted. Finally, the recently introduced In-GaAs/AlGaAs MODFET's are shown to have switching speeds superior to those of conventional GaAs/AlGaAs MODFET's.     

Drain current dlts analysis of recoverable and permanent degradation effects in AlGaAs/GaAs AND AlGaAs/InGaAs HEMT'S

We present a detailed study of drain current DLTS spectra performed on asreceived and failed AlGaAs/GaAs and AlGaAs/InGaAs HEMT's of four different suppliers submitted to hot-electron tests. We demonstrate that a remarkable correlation exists between DLTS features and permanent and recoverable degradation effects. In particular, different behaviours have been found: (i) recoverable effects seems to be correlated with modulation of charge trapped on DX and ME6 centers. (ii) permanent degradation consisting in a decrease in Id and V_T is due to negative charge trapping and is associated with a large increase of a peak having Ea=1.22 eV in the DLTS spectra of failed devices; (iii) development of traps in the gate-to-drain access region induces a permanent increase in drain parasitic resistance Rd and decrease in Id, and is correlated with the growth of a “hole-like” peak in DLTS spectra measured after hot-electron tests.     

双平面掺杂AlGaAs／InGaAs功率PHEMT

双平面掺杂ＡｌＧａＡｓ／ＩｎＧａＡｓ功率ＰＨＥＭＴ陈效建，刘军，李拂晓，郑雪帆，华培忠（南京电子器件研究所，２１００１６）Ｄｏｕｂｌｅ－ｐｌａｎａｒ－ｄｏｐｅｄＡｌＧａＡｓ／ＩｎＧａＡｓＰｏｗｅｒＰＨＥＭＴ￥ＣｈｅｎＸｉａｏｊｉａｎ；ＬｉｕＪｕｎ；Ｌ...     

Improved model for kink effect in AlGaAs/InGaAs heterojunctionFET's

The kink effect in an AlGaAs/InGaAs HJFET has been investigated with regard to optical wavelength, temperature and gate voltage. The study reveals that the drain current value measured at the drain voltage lower than the kink voltage increases by irradiating white light onto the device, indicating the irradiation-induced kink effect recovery. The degree of the kink disappearance exhibited a significant optical wavelength dependence. We also found that the kink effect is suppressed either by increasing the temperature or by applying a high gate voltage where parallel conduction takes place. Based on these experimental results, we propose an improved model for the kink effect in an AlGaAs/InGaAs HJFET in which the kink effect is closely related to carrier trapping at the hole traps in the AlGaAs donor layer     

Double-side planar-doped AlGaAs/InGaAs/AlGaAs MODFET with currentdensity of 1 A/mm

AlGaAs/InGaAs/AlGaAs double-side planar-doped (DSPD) pseudomorphic MODFETs of 0.3-μm gate length with both excellent DC and RF performances are reported. A maximum unilateral gain cutoff frequency of 170 GHz and a maximum current gain cutoff frequency of 60 GHz are achieved. The devices exhibit a maximum transconductance of 500 mS/mm and an extremely high current density of 1 A/mm. These are the highest frequencies reported so far for MODFET devices capable of driving 1-A/mm current density. This current density is the highest ever reported with this type of layer structure     

A high-current pseudomorphic AlGaAs/InGaAs double quantum-wellMODFET

Double quantum-well modulation-doped field-effect transistors (MODFETs) with planar-doped lattice-strained AlGaAs/InGaAs structure have been fabricated and characterized at DC and microwave frequencies. At 300 K the 0.3-μm gate devices show a full channel current of 1100 mA/mm with a constant extrinsic transconductance of 350 mS/mm over a broad gate voltage range of 1.6 V. Excellent microwave performance is also achieved with a maximum available gain cutoff frequency f _mag of 110 GHz and a current gain cutoff frequency f _r of 52 GHz. A maximum output power of 0.7 W/mm with 30% efficiency is obtained at 18 GHz     

InGaAs/AlGaAs半导体激光器二维阵列

用金属有机化合物气相淀积 (MOCVD)技术外延生长了InGaAs/AlGaAs分别限制应变单量子阱激光器材料。利用该材料制成半导体激光器一维线阵列 ,然后再串联组装成二维阵列 ,在 1 0 0 0 μs的输入脉宽下 ,输出峰值功率达到 730W (77A) ,输出光功率密度为 4 87W/cm2 ,中心激射波长为 90 3nm ,光谱半宽 (FWHM )为 4 4nm。在此条件下可以稳定工作 86 0 0h以上     

InGaAs/GaAs/AlGaAs应变量子阱激光器

优化设计了既能实现较小垂直方向远场发散角,又能降低腔面光功率密度的ＩｎＧａＡｓ／ＧａＡｓ／ＡｌＧａＡｓ应变层量子阱激光器,并计算了该结构激光器实现基横模工作的脊形波导结构参数。利用分子束外延生长了ＩｎＧａＡｓ／ＧａＡｓ／ＡｌＧａＡｓ应变量子阱激光器材料并研制出基横模输出功率大于１４０ｍＷ,激射波长为９８０ｎｍ的脊形波导应变量子阱激光器,其微分量子效率为０．８Ｗ／Ａ,垂直和平行结平面方向远场发散角分别为２８°和６．８°     

High performance BCB-bridged AlGaAs/InGaAs power HFETs

A novel low-k benzocyclobutene (BCB) bridged and passivated layer for AlGaAs/InGaAs doped-channel power field effect transistors (FETs) with high reliability and linearity has been developed and characterized. In this study, we applied a low-k BCB-bridged interlayer to replace the conventional air-bridged process and the SiN/sub x/ passivation technology of the 1 mm-wide power device fabrication. This novel and easy technique demonstrates a low power gain degradation under a high input power swing, and exhibits an improved adjacent channel power ratio (ACPR) than those of the air-bridged one, due to its lower gate leakage current. The power gain degradation ratio of BCB-bridged devices under a high input power operation (P/sub in/ = 5 /spl sim/ 10 dBm) is 0.51 dB/dBm, and this value is 0.65 dB/dBm of the conventional air-bridged device. Furthermore, this novel technology has been qualified by using the 85-85 industrial specification (temperature = 85 C, humidity = 85%) for 500 h. These results demonstrate a robust doped-channel HFET power device with a BCB passivation and bridged technology of future power device applications.     

The power density giving rise to optical degradation of mirrors in InGaAs/AlGaAs/GaAs-based laser diodes

The InGaAs/AlGaAs/GaAs double laser heterostructures of separate confinement with a quantum well were formed by molecular-beam epitaxy. The study of characteristics of laser diodes with a wide contact (100 μm) showed that the power corresponding to the catastrophic degradation of mirrors may attain nearly the highest values ever achieved (20 MW/cm²) that were previously obtained for laser diodes based on InGaAsP/GaAs heterostructures alone. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 11, 2000, pp. 1394–1395. Original Russian Text Copyright ? 2000 by Kotel’nikov, Katsnel’son, Kudryashov, Rastegaeva, Richter, Evtikhiev, Tarasov, Alferov.     

Characterization of InGaAs/AlGaAs pseudomorphic modulation-doped field-effect transistors

High-performance pseudomorphic InyGa1-yAs/Al0.15- Ga0.85As (0.05 le y le 0.2) MODFET's grown by MBE have been characterized at dc (300 and 77 K) and RF frequencies. Transconductances as high as 310 and 380 mS/mm and drain currents as high as 290 and 310 mA/mm were obtained at 300 and 77 K, respectively, for 1-µm gate lengths and 3-µm source-drain spacing devices. Lack of persistent trapping effects,I-Vcollapse, and threshold voltage shifts observed with these devices are attributed to the use of low mole fraction AlxGa1-xAs while still maintaining 2DEG concentrations of about 1.3 × 10¹²cm^-2. Detailed microwave S-parameter measurements indicate a current gain cut-off frequency Of 24.5 GHz Wheny = 0.20, which is as much as 100 percent better than similar GaAs/AlGaAs MODFET structures, and a maximum frequency of oscillation of 40 GHz. These superior results are in part due to the higher electron velocity of InGaAs as compared with GaAs. Velocity field measurement performed up to 3 kV/cm using the magnetoresistance method indicates an electron saturation velocity of greater than 1.7 × 10⁷cm/s at 77 K fory = 0.15, which is 20 percent higher than GaAs/AlGaAs MODFET's of similar structure.     

High-contrast/low-voltage normally on InGaAs/AlGaAs asymmetricFabry-Perot modulator

An asymmetric Fabry-Perot cavity modulator is proposed with a 50-period In_0.15Ga_0.85As/Al_0.30Ga_0.70 As strained-layer superlattice active layer. The back Bragg reflector consists of 25 periods of GaAs/AlAs layers while for the front reflector of the device the natural reflection of the air-semiconductor interface was used. Spectral measurements as a function of the applied reverse voltages showed a change in reflectivity from 33% for 0 V reverse bias to 5% for 7 V, at a wavelength of 969 nm. This gives a maximum contrast ratio of 8.3 dB and an insertion loss of 4.9 dB. For higher voltages applied across the device, the reflectivity increases again     

A new empirical large-signal model for enhancement-mode AlGaAs/InGaAs pHEMTs

We propose a new large-signal model for AlGaAs/InGaAs pHEMTs, which can simulate the device microwave output power, non-linear characteristics at arbitrary bias points. This model includes a new drain current equation, which is extracted from its derivatives. In addition, gate-to-source and gate-to-drain capacitances are also characterized versus the function of gate and drain biases. The parameter extraction procedure is addressed for the enhancement-mode pHEMTs, which offers an attractive solution for handset power amplifier application because of its positive bias characteristics. Finally, measured and model-predicted dc I–V, S-parameters, and power performance have been compared.     

AlGaAs/InGaAs/GaAs quantum-well power MISFET at millimeter-wavefrequencies

An AlGaAs/InGaAs/GaAs quantum-well MISFET developed for power operation at millimeter-wave frequencies is described. The InGaAs channel is heavily doped to increase the sheet carrier density, resulting in a maximum current density of 700 mA/mm with a transconductance of 480 mS/mm. The 0.25-μm×50-μm device delivers a power density of 0.76 W/mm with 3.6-dB gain and 19% power-added efficiency at 60 GHz. At 5.2 dB gain, the power density is 0.55 W/mm. A similar device built on an undoped InGaAs channel had much poorer power performance and no speed advantage