Al/sub 0.25/Ga/sub 0.75/As/In/sub 0.25/Ga/sub 0.75/As pseudomorphic MODFET with high DC and RF performance

AlGaAs/InGaAs MODFETs having 25% indium in the channel and L/sub G/=0.35 mu m have been fabricated. From DC device characterisation, a maximum saturation current of 670 mA/mm and an extrinsic transconductance of 500 mS/mm have been measured. A maximum unilateral gain cutoff frequency of f/sub c/=205 GHz and a maximum current gain cutoff frequency of f/sub T/=86 GHz have been achieved. Bias dependence of f/sub c/ and f/sub T/ has been measured. At 12 GHz a minimum noise figure of NF=0.8 dB and an associated gain of 11 dB have been measured.<>     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

Submicron-gate ion-implanted In/sub 0.15/Ga/sub 0.85/As/GaAs MESFETs with graded indium composition

0.25 mu m and 0.5 mu m gate ion-implanted MESFETs have been fabricated on In/sub 0.15/Ga/sub 0.85/As epitaxial layers. These layers are grown by MOCVD on three inch diameter GaAs substrates with the indium mole fraction graded from 15% at the InGaAs/GaAs heterointerface to 0% at the surface. Both devices show excellent DC and microwave performance. From S-parameter measurements, extrinsic current gain cutoff frequencies f/sub t/ of 120 and 61 GHz are obtained for the 0.25 mu m and 0.5 mu m gate MESFETs, respectively. The authors investigate the potential of small-bandgap InGaAs materials for submicron-gate MESFET applications.<>     

Type I and Type II Alignment of the Light Hole Band in In0.15Ga0.85As/GaAs and in ln0.15Ga0.85As/Al0.15Ga0.85As Strained Quantum Wells

We present results of photoluminescence and cathodoluminescence measurements of strained undoped In_0.15Ga_0.85As/GaAs and In_0.15Ga_0.85As/Al_0.15Ga_0.85As quantum well structures, designed to throw light on the current controversy over light-hole band alignment at low In content. We compare these data with theoretical calculations of the confined state energies within the eight band effective mass approximation. Our analysis shows that for In_0.15Ga_0.85As/GaAs, the observed two transitions are consistent with either type I or type II alignment of the light hole band for band offset ratios within the accepted range. In the case of In_0.15Ga_0.85As/Al_0.15Ga_0.85As, however, our results clearly indicate type II alignment for the light hole band. We derive the band offset ratio Q, defined here as Q = δE_c/δE_g where δE_c is the conduction band offset and δE_g is the bandgap difference between the quantum well and the barrier in the presence of strain, for the In_0.15Ga_0.85As/Al_0.15Ga_0.85As system to be Q = 0.83 and discuss it in the context of the common anion rule.     

Ga/sub 0.8/In/sub 0.2/As/GaAs/Ga/sub 0.51/In/sub 0.49/P buried ridge structure single quantum well laser emitting at 0.98 mu m

The first fabrication is reported of a buried ridge structure Ga/sub 0.8/In/sub 0.2/As/GaAs/Ga/sub 0.51/In/sub 0.49/P laser emitting at 0.98 mu m grown by two-step low pressure metal organic chemical vapour deposition. The width of the ridge is 2 mu m. Laser output power greater than 40 mW with a threshold current of 30 mA has been measured. A typical quantum efficiency of eta =60% was obtained without any facet coating. Excellent homogeneity and uniformity have been achieved over a wafer area of 10 cm/sup 2/.<>     

0.5 mu m gate length InP/In/sub 0.75/Ga/sub 0.25/As/InP pseudomorphic HEMT with high DC and RF performance

High performance InP/In/sub 0.75/Ga/sub 0.25/As/InP pseudomorphic double heterojunction (DH) HEMTs with a gate length of 0.5 mu m are reported. Both DC and RF characteristics of this new type of Al-free HEMT demonstrate its suitability for microwave applications.<>     

A new Pt/oxide/In/sub 0.49/Ga/sub 0.51/P MOS Schottky diode hydrogen sensor

A new and interesting Pt/oxide/In/sub 0.49/Ga/sub 0.51/P metal-oxide-semiconductor (MOS) Schottky diode hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations and at different temperatures are measured. The presence of dipoles at the oxide layer leads to an extra electrical field and the variation of Schottky barrier height. Even at room temperature, a very high hydrogen detection sensitivity of 561% is obtained when a 9090 ppm H/sub 2//air gas is introduced. In addition, an absorption response time less than 1 s under the applied voltage of 0.7 V and 9090 ppm H/sub 2//air hydrogen ambient is found. The roles of hydrogen adsorption and desorption for the transient response at different temperatures are also investigated.     

Vertical integration of an In/sub 0.15/Ga/sub 0.85/As modulation-doped field effect transistor and GaAs laser grown by molecular beam epitaxy

A vertically integrated structure consisting of an In/sub 0.15/Ga/sub 0.85/As pseudomorphic modulation doped field effect transistor (MODFET) and a GaAs graded index separate confinement heterostructure single quantum well (GRINSCH SQW) laser was grown by molecular beam epitaxy. Wafers containing integrated MODFET/laser layers produced MODFETs with DC and microwave performance comparable to wafers containing only MODFET layers, indicating that the modulation doping and the strained In/sub 0.15/Ga/sub 0.85/As channel were largely unaffected by the long, high temperature laser growth. The lasers had threshold currents similar to identical structures grown on n-type substrates and the integrated structures had a -3dB modulation bandwidth of 3.5 GHz.<>     

Analysis of Al0.15Ga0.85N/GaN/Al0.15Ga0.85N DH-HEMT for RF and Microwave Frequency Applications

Semiconductors - A charge control based analytical model is followed to study the impact of donor-layer doping and gate-length on microwave frequency performance of AlGaN/GaN/AlGaN double...     

The microwave power performance comparisons of Al/sub x/Ga/sub 1-x/As/In/sub 0.15/Ga/sub 0.85/As (x=0.3, 0.5, 0.7, 1.0) doped-channel HFETs

The properties of doped-channel field-effect transistors (DCFET) have been thoroughly investigated on Al/sub x/Ga/sub 1-x/As/InGaAs (x= 0.3, 0.5, 0.7, 1) heterostructures with various Al mole fractions. In this study, we observed that by introducing a 200-/spl Aring/-thick Al/sub 0.5/Ga/sub 0.5/As (x=0.5) Schottky layer can enhance the device power performance, as compared with the conventional x=0.3 AlGaAs composition system. However, a degradation of the device power performance was observed for further increasing the Al mole fractions owing to their high sheet resistance and surface states. Therefore, Al/sub 0.5/Ga/sub 0.5/As Schottky layer design provides a good opportunity to develop a high power device for power amplifier applications.     

Ga0.51In0.49P/In0.15Ga0.85As/GaAs pseudomorphic doped-channel FET with high-current densityand high-breakdown voltage

Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs pseudomorphic doped-channel FETs exhibiting excellent DC and microwave characteristics were successfully fabricated. A high peak transconductance of 350 mS/mm, a high gate-drain breakdown voltage of 31 V and a high maximum current density (575 mA/mm) were achieved. These results demonstrate that high transconductance and high breakdown voltage could be attained by using In_0.15Ga_0.85As and Ga_0.51In_0.49P as the channel and insulator materials, respectively. We also measured a high-current gain cut-off frequency f_t of 23.3 GHz and a high maximum oscillation frequency f_max of 50.8 GHz for a 1-μm gate length device at 300 K. RF values where higher than those of other works of InGaAs channel pseudomorphic doped-channel FETs (DCFETs), high electron mobility transistors (HEMTs), and heterostructure FETs (HFETs) with the same gate length and were mainly attributed to higher transconductance due to higher mobility, while the DC values were comparable with the other works. The above results suggested that Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs doped channel FET's were were very suitable for microwave high power device application     

Characteristics of In/sub 0.425/Al/sub 0.575/As-InxGa/sub 1-x/As metamorphic HEMTs with pseudomorphic and symmetrically graded channels

In/sub 0.425/Al/sub 0.575/As-In/sub x/Ga/sub 1-x/As metamorphic high electron mobility transistors (MHEMTs) with two different channel designs, grown by molecular beam epitaxy (MBE) system, have been successfully investigated. Comprehensive dc and high-frequency characteristics, including the extrinsic transconductance, current driving capability, device linearity, pinch-off property, gate-voltage swing, breakdown performance, unity-gain cutoff frequency, max. oscillation frequency, output power, and power gain, etc., have been characterized and compared. In addition, complete parametric information of the small-signal device model has also been extracted and discussed for the pseudomorphic channel MHEMT (PC-MHEMT) and the V-shaped symmetrically graded channel MHEMT (SGC-MHEMT), respectively.     

Pseudomorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.7/Ga/sub 0.3/As HEMTs with an ultrahigh f/sub T/ of 562 GHz

We fabricated decananometer-gate pseudomorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.7/Ga/sub 0.3/As high-electron mobility transistors (HEMTs) with a very short gate-channel distance. We obtained a cutoff frequency f/sub T/ of 562 GHz for a 25-nm-gate HEMT. This f/sub T/ is the highest value ever reported for any transistor. The ultrahigh f/sub T/ of our HEMT can be explained by an enhanced electron velocity under the gate, which was a result of reducing the gate-channel distance.     

Self-aligned In0.49Ga0.51P/GaAs HBT DC and RF characteristics related with orientations

A self-aligned InGaP/GaAs HBT DC and RF characteristics related with orientations were studied. The DC current gain was greater for the [0 1 1] emitter orientation compared to orientation. However, it also showed slightly better RF performance for orientation with a cutoff frequency f_T 69 GHz compared to the f_T of 62 GHz for the [0 1 1] orientation. This experimental work has been proposed that the dependence of the characteristics could be attributed to both piezoelectric effect and the difference between lateral etched profiles in different directions.     

Effect of strain on microwave noise characteristics in In/sub 0.52/Al/sub 0.48/As/In/sub x/Ga/sub 1-x/As (0.53

Chough  K.B. Hong  W.-P. Florez  L. Song  J.I. 《Electronics letters》1993,29(15):1338-1340

Device linearity comparison of uniformly doped and /spl delta/-doped In/sub 0.52/Al/sub 0.48/As/In/sub 0.6/Ga/sub 0.4/As metamorphic HEMTs

The uniformly doped and the /spl delta/-doped In/sub 0.52/Al/sub 0.48/As/In/sub 0.6/Ga/sub 0.4/As metamorphic high-electron mobility transistors (MHEMTs) were fabricated, and the dc characteristics and the third-order intercept point (IP3) of these devices were measured and compared. Due to more uniform electron distribution in the quantum-well region, the uniformly doped MHEMT exhibits a flatter transconductance (G/sub m/) versus drain-to-source current (I/sub DS/) curve and much better linearity with higher IP3 and higher IP3-to-P/sub dc/ ratio as compared to the /spl delta/-doped MHEMT, even though the /spl delta/-doped device exhibits higher peak transconductance. As a result, the uniformly doped MHEMT is more suitable for communication systems that require high linearity operation.     

DC and RF Characteristics of 0.15 pm Power Metamorphic HEMTs

DC and RF characteristics of 0.15 °m GaAs power metamorphic high electron mobility transistors (MHEMT) have been investigated. The 0.15 °m ° 100 °m MHEMT device shows a drain saturation current of 480 mA/mm, an extrinsic transconductance of 830 mS/mm, and a threshold voltage of ‐0.65 V. Uniformities of the threshold voltage and the maximum extrinsic transconductance across a 4‐inch wafer were 8.3% and 5.1%, respectively. The obtained cut‐off frequency and maximum frequency of oscillation are 141 GHz and 243 GHz, respectively. The 8 ° 50 °m MHEMT device shows 33.2% power‐added efficiency, an 18.1 dB power gain, and a 28.2 mW output power. A very low minimum noise figure of 0.79 dB and an associated gain of 10.56 dB at 26 GHz are obtained for the power MHEMT with an indium content of 53% in the InGaAs channel. This excellent noise characteristic is attributed to the drastic reduction of gate resistance by the T‐shaped gate with a wide head and improved device performance. This power MHEMT technology can be used toward 77 GHz band applications.     

发射极镇流电阻对In0.49Ga0.51P/GaAsHBT特性的影响

在发射极加一个镇流电阻可以解决在多个HBT并联时,常常出现电流坍塌的问题.研究了发射极镇流电阻对In0.49Ga0.51P/GaAs HBT直流及高频特性的影响,并对实验现象进行了理论分析.     

Comparing GaAs and In0.15Ga0.85As as channel material for alternative substrate CMOS

Photoluminescence intensity (PLI) measurements of GaAs and InGaAs thin films indicate that InGaAs might be inherently easier to passivate than GaAs. The introduction of just 15% of In leads to a reduction of the surface recombination velocity at native oxide interfaces by an order of magnitude. This is more than the effect expected by a reduced bandgap alone. The PLI method applied to thin films can also be used to determine the surface recombination velocity of other IIIV-oxide interfaces.     

发射极镇流电阻对In_(0.49)Ga_(0 .51)P/GaAs HBT特性的影响

在发射极加一个镇流电阻可以解决在多个HBT并联时,常常出现电流坍塌的问题.研究了发射极镇流电阻对In0.49Ga0.51P/GaAs HBT直流及高频特性的影响,并对实验现象进行了理论分析.