Low-frequency noise in p-channel heterostructure insulated-gatefield-effect transistors (HIGFETs) at 77 K and drain current 1μA

Measurements of the low-frequency spectral intensity of the current fluctuations in p-channel GaAs/AlGaAs heterostructure insulated-gate field-effect transistors are discussed. The measurements were performed at 77 K and a drain current of 1 μA. The spectra of two types of devices are compared, one grown directly on the substrate and the other embedded in an n-well. The latter type produced markedly less noise, its spectrum being almost perfect 1/f noise. The former type exhibited, in addition to the 1/f noise, a significant generation-recombination noise component in the spectrum     

AlInAs/GaInAs heterostructure bipolar transistors grown by metalorganic chemical vapour deposition

Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.47/In/sub 0.53/As heterostructure bipolar transistors are demonstrated using metalorganic chemical vapour deposition. The transistors have a cutoff frequency of 80 GHz and a common-emitter breakdown voltage of 5.5 V.<>     

High transconductance selfaligned WSi gate AlInAs/GaInAs HIGFETs grown by MOCVD

HIGFETs were fabricated using an AlInAs/GaInAs heterostructure grown by MOCVD. The 1 mu m-gate HIGFET showed a maximum transconductance of 740 mS/mm at room temperature, which is the highest transconductance obtained for HIGFETs. The reduction of the AlInAs layer thickness to 30 nm and the low source resistance are the primary reasons for this enhancement.<>     

Reliability of AlInAs/GaInAs heterojunction bipolar transistors

The reliability of high-performance AlInAs/GaInAs heterojunction bipolar transistors (HBTs) grown by molecular beam epitaxy (MBE) is discussed. Devices with a base Be doping level of 5×10¹⁹ cm^-3 and a base thickness of approximately 50 nm displayed no sign of Be diffusion under applied bias. Excellent stability in DC current gain, device turn-on voltage, and base-emitter junction characteristics was observed. Accelerated life-test experiments were performed under an applied constant collector current density of 7×10⁴ A/cm² at ambient temperatures of 193, 208, and 328°C. Junction temperature and device thermal resistance were determined experimentally. Degradation of the base-collector junction was used as failure criterion to project a mean time to failure in excess of 10⁷ h at 125°C junction temperature with an associated activation energy of 1.92 eV     

Low-frequency noise characteristics of AlInAs/GaInAs modulation-doped field-effect transistors

The output noise voltage of AlInAs/GaInAs MODFETs grown by both MOCVD and MBE was measured at frequencies from 1 MHz to 1.5 GHz under different bias conditions for the first time. For frequencies below 500 MHz the noise voltage showed a 1/f dependence with a corner frequency around 200 MHz. The low-frequency noise was larger at the bias conditions giving higher transconductance.<>     

50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electronmobility transistors

The design and fabrication of a class of 50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electron mobility transistors (HEMTs) with potential for ultra-high-frequency and ultra-low-noise applications are reported. These devices exhibit an extrinsic transconductance of 1740 mS/mm and an extrinsic current-gain cutoff frequency of 340 GHz at room temperature. The small-signal characteristics of a pseudomorphic and a lattice-matched AlInAs/GaInAs HEMT with similar gate length (50 nm) and gate-to-channel separation (17.5 nm) are compared. The former demonstrates a 16% higher transconductance and a 15% higher current-gain cutoff frequency, but exhibits a 38% poorer output conductance. An analysis of the high-field transport properties of ultra-short gate-length AlInAs/GaInAs HEMTs shows that a reduction of gate length from 150 to 50 nm neither enhances nor reduces their average velocity. In contrast, the addition of indium from 53% to 80% improves this parameter by 19%     

Gate leakage current in GaN-based mesa- and planar-type heterostructure field-effect transistors

The excessive gate leakage current of the planar- and mesa-type InAlN/GaN heterostructure field-effect transistors (HFETs) is evaluated. It is found that the gate current of the mesa-type HFETs is higher than that of the planar devices, particularly at low biases. Analyses of the gate current considering different transport mechanisms yielded identical thermionic currents (i.e., an identical Schottky barrier height) but a significantly higher leakage component in the mesa-type HFETs than in the planar devices. This additional current component observed in the mesa-type devices shows a nearly ohmic behavior. Mapping by the electron-beam induced current technique confirms an enhanced current located under the expanded gate contact and on the part of the mesa-sidewall, where the gate contact is placed. Two-dimensional simulation of the device structure shows that considerable part of the gate leakage current flows through the GaN buffer layer. These results underline the importance of a proper design of the device structure and layout (i.e., the use of planar structure with device insulation prepared by ion implantation rather than by mesa technique), and of the preparation of the GaN buffer (it should be semi-insulating) in order to fabricate reliable, low leakage current GaN-based HFETs.     

Emitter injection and collector current ideality in abrupt heterojunction AlInAs/GaInAs HBTs

We investigated the electron injection process for high-speed N-p-n AlInAs/GaInAs HBTs by measuring collector and base currents as a function of base-emitter voltage with collector-base voltage equal to zero (Gummel plots) at temperatures from 77 to 300 K. We compared the measured collector current with calculations based on electron injection from emitter to base by tunneling through the conduction band spike and thermionic emission over it, using a modified version of the thermionic-field emission theory developed by Crowell and Rideout. Good agreement was obtained between the experimental collector current ideality factor and tunneling-thermionic emission theory for all temperatures and currents. This is an improvement over drift-diffusion and thermionic emission models, which have been used for HBTs but which do not correctly describe the experimentally observed temperature and current dependence of the ideality of the collector current. The tunneling-thermionic emission model explains the increase in collector current ideality factor that occurs as the transistor is biased at high collector current density (J_C 10⁵ A cm⁻²), which is the regime of operation in which f_T is maximized and a low ideality factor is most important. The model also explains the experimentally observed variation of h_FE with ln I_C. Thus the tunneling-thermionic emission model is a useful aid in the design of the epitaxial structure for high-frequency HBTs.     

V-band high-efficiency high-power AlInAs/GaInAs/InP HEMT's

The authors report on the state-of-the-art power performance of InP-based HEMTs (high electron mobility transistors) at 59 GHz. Using a 448-μm-wide HEMT with a gate length of 0.15 μm, an output power of 155 mW with a 4.9-dB gain and a power-added efficiency of 30.1% were obtained. By power-combining two of these HEMTs, an output power of 288 mW with 3.6-dB gain and a power-added efficiency of 20.4% were achieved. This is the highest output power reported with such a high efficiency for InP-based HEMTs, and is comparable to the best results reported for AlGaAs/InGaAs on GaAs pseudomorphic HEMTs at this frequency     

High-breakdown-voltage AlInAs/GaInAs junction-modulated HEMT's(JHEMT's) with regrown ohmic contacts by MOCVD

A technology for increasing both the two-terminal gate-drain breakdown and subsequently the three-terminal-off-state breakdown of AlInAs/GaInAs high-electron-mobility transistors (HEMTs) to record values without substantial impact on other parameters is presented. The breakdown in these structures is dependent on the multiplication of electrons injected from the source (channel current) and the gate (gate leakage) into the channel. In addition, holes are generated by high fields at the drain and are injected back into the gate and source electrodes. These phenomena can be suppressed by increasing the gate barrier height and alleviating the fields at the drain. Both have been achieved by incorporating a p⁺-2DEG junction as the gate that modulates the 2DEG gas and by utilizing selective regrowth of the source and drain regions by MOCVD. The 1-μm-gate-length devices fabricated have two-terminal gate-drain and three-terminal-off-state breakdown voltages of 31 V and 28 V, respectively     

Semiconductor-gated InGaAs/InAlAs heterostructure transistors (SISFET's)

We have successfully fabricated FET's with In0.53Ga0.47As channels, lattice-matched In0.52Al0.48As gate barriers, and n+ In0.53- Ga0.47As gates. For a barrier thickness of 600 Å and a gate length of 1.7 µm, the maximum transconductance is 250 mS/mm at T = 300 K. From gate capacitance measurements, the cutoff frequency is inferred to be ft= 15 GHz for this gate length. Self-aligned source and drain implants have been used to permit nonalloyed ohmic contacts with a characteristic resistance of 0.1 Ω.mm. The transconductance remains above 210 mS/mm for forward gate bias up to +1.0 V, confirming the usefulness of this gate structure for enhancement-mode devices.     

Double junction AlInAs/GaInAs multiquantum well avalanche photodiodes

A separate absorption, grading, and multiplication avalanche photodiode with an AlInAs/GaInAs multiquantum well multiplication region is reported. This device exhibits a low excess-noise factor and a gain-bandwidth product of 50 GHz, due to the high ratio of ionisation rates of the multiplication material. In addition, a large bandwidth is obtained owing to the use of an undoped (n type) GaInAs absorption layer, fully depleted when multiplication occurs.<>     

A model-based comparison of AlInAs/GaInAs and InP/GaInAs HBT's: aMonte Carlo study

The high-speed performances of AlInAs/GaInAs and InP/GaInAs heterojunction bipolar transistors (HBTs) are investigated using a one-dimensional self-consistent particle simulator. Optimum alloy compositions for a graded-gap base structure are obtained for both transistors through the tradeoff between the emitter-charging time and base transit time. The saturation velocity in the GaInAs n-type collector is found to be smaller than that in InP, which has been attributed to the diffusion of a large number of hot back-scattered Γ-valley electrons in the GaInAs collector. The difference in the collector transit time in p-type collectors is trivial, since the maximum electron velocity was restricted to below 1.2×10⁸ cm/s due to a strong nonparabolicity effect. The cutoff frequency for the former and the latter are estimated to be 2 and 1.5 times higher, respectively, than for AlGaAs/GaAs HBTs. These results are attributed to a larger bandgap difference between the emitter and base, to yield a high base built-in field, rather than a larger Γ-L band separation energy in the collector to enhance the velocity overshoot effect     

Metamorphic AlInAs/GaInAs HEMTs on GaAs Substrates by MOCVD

Metamorphic AlInAs/GaInAs high-electron mobility transistors with very good device performance have been grown by metal-organic chemical vapor deposition (MOCVD), with the introduction of an effective multistage buffering scheme. Measured room-temperature Hall mobilities of the 2-DEG were over 8000 cm²/V ldr s with sheet carrier densities larger than 4 times 10¹² cm^-2. Transistors with 1-mum gate length exhibited transconductance up to 626 mS/mm. The unity current gain cutoff frequency f_T and the maximum oscillation frequency f_max were 39.1 and 71 GHz, respectively. These results are very encouraging toward the manufacturing of metamorphic devices on GaAs substrates by MOCVD.     

39.5-GHz static frequency divider implemented in AlInAs/GaInAs HBTtechnology

A static divide-by-4 frequency divider operating at 39.5 GHz with a corresponding gate delay of 12.6 ps was implemented using InP-based HBT technology. The AlInAs/GaInAs HBT devices utilized in the divider incorporated a graded emitter-base (E-B) junction and had a unity gain cutoff frequency, maximum frequency of oscillation, and current gain β of 130 GHz, 91 GHz, and 39, respectively. The divider was operated with a 3-V power supply and consumed a total power of 425 mW (77 mW per flip-flop). The divider functional yield was over 90%. The operating frequency of this circuit is the highest ever reported for a static divider     

A high-speed eight-channel optoelectronic integrated receiver arraycomprising GaInAs p-i-n PD's and AlInAs/GaInAs HEMTs

The successful fabrication of an eight-channel optoelectronic integrated receiver array on an InP substrate, which comprises eighty elements including GaInAs p-i-n photodiodes (PDs) and AlInAs/GaInAs HEMTs, is reported. An average bandwidth of 1.2 GHz with a standard deviation of 190 MHz over the whole channel was obtained. An average responsivity was 546 V/W with a standard deviation of only 19.2 V/W. A crosstalk was less than -30 dB at frequencies between 3 and 900 MHz and as small as -28 dB even at 1 GHz. The yield of chips available for 1.0 Gb/s operation was as high as 62.5% over 2-in-diameter wafer     

Kink-free AlInAs/GaInAs/InP HEMTs grown by molecular beam epitaxy

Kink-free AlInAs/GaInAs/InP HEMTs have been fabricated from an MBE structure grown under normal growth condition. Devices with 1 mu m gate-length exhibit an extrinsic transconductance of 450 mS/mm and a maximum drain current of 600 mA/mm which represent the best results for 1 mu m gate devices. The DC output conductance shows no kink over the entire gate bias range. The elimination of the kink is attributed to the high quality AlInAs buffer layer and a low mismatch between the AlInAs buffer layer and InP substrate.<>     

High reliability planar-type GaInAs/InP heterostructure avalanchephotodiodes

High-temperature, long-term life tests of GaInAs/InP heterostructure avalanche photodiodes have been carried out to establish criteria for high reliability photodetectors in 1.55 μm-wavelength optical submarine cable systems. A failure rate of less than 0.2 FIT at 10°C was predicted for the first time with an activation energy of 0.7 eV     

GaInAs／AlInAs调制掺杂结构材料的光学性质研究

研究了ＧａＩｎＡｓ／ＡｌＩｎＡｓｎ型调制掺杂结构样品的光致发光及其激发光谱。当空穴态被局域化后．二维电子气的发光线形反映了导带二维态密度的填充效应：导带两个子带填充电子。发光强度则表明，导带第二子带电子波函数在空间上更扩展，与空间分离的空穴产生发光复合的几率较大。激发光谱提供了样品中异质结结构直接带边附近光吸收过程的信息。