Heterostructure Insulated-gate Field-effect Transistors Research Articles

Gate-length dependence of DC and microwave properties of submicrometer In/sub 0.53/Ga/sub 0.47/As HIGFETs

In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As/InP heterostructure insulated-gate field-effect transistors (HIGFETs) with gate lengths from 1.1 and 0.3 mu m have been fabricated, and their electrical performance is characterized at DC and microwave frequencies. The refractory-gate self-aligned process, applied to devices with In/sub 0.53/Ga/sub 0.47/As channels, yields an unprecedented combination of very-high speed and excellent uniformity. HIGFETs with L/sub g/=0.6 mu m showed average peak transconductance g/sub m/ of 528 mS/mm and unity-current-gain cutoff frequency f/sub t/ of 50 GHz. The uniformity of g/sub m/ was better than 1%, and the voltage of the g/sub m/ peak was uniform to +or-30 mV. HIGFETs with L/sub g/=0.3 mu m showed f/sub 1/ up to 63 GHz, but suffered from serious short-channel effect, due to excessive thickness of the InGaAs channel layer. A self-aligned technique for gate resistance reduction is shown to substantially improve microwave power gain. >

Quantum-well p-channel AlGaAs/InGaAs/GaAs heterostructure insulated-gate field-effect transistors with very high transconductance

Quantum-well p-channel pseudomorphic AlGaAs/InGaAs/GaAs heterostructure insulated-gate field-effect transistors with enhanced hole mobility are described. The devices exhibit room-temperature transconductance, transconductance parameter, and maximum drain current as high as 113 mS/mm, 305 mS/V/mm, and 94 mA/mm, respectively, in 0.8- mu m-gate devices. Transconductance, transconductance parameter, and maximum drain current as high as 175 mS/mm, 800 mS/V/mm, and 180 mA/mm, respectively were obtained in 1- mu m p-channel devices at 77 K. From the device data hole field-effect mobilities of 860 cm/sup 2//V-s at 300 K and 2815 cm/sup 2//V-s at 77 K have been deduced. The gate current causes the transconductance to drop (and even to change sign) at large voltage swings. Further improvement of the device characteristics may be obtained by minimizing the gate current. To this end, a type of device structure called the dipole heterostructure insulated-gate field-effect transistor is proposed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A new and simple model for GaAs heterojunction FET gate characteristics

The gate current-voltage characteristics for modulation-doped field-effect transistors (MODFETs) and heterostructure insulated-gate field-effect transistors (HIGFETs) are described using a simple model. This model, which is physically realistic, consists of two Schottky diodes in series: one is a metal-semiconductor (AlGaAs) Schottky diode and the other is an equivalent Schottky diode due to the heterojunction between the AlGaAs and GaAs. A novel technique is developed to characterize the parameters used for this model. The model is used to estimate the effective electron temperature in the channel close to the drain for MODFETs. The estimated electron temperature with 1 V drain-to-source voltage is as high as 80 degrees C at room temperature. Very good agreement between the calculated and measured results is obtained. This model and characterization technique are also suitable for other heterojunction FETs such as quantum-well MODFETs, etc.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Current-voltage and capacitance-voltage characteristics of heterostructure insulated-gate field-effect transistors

We present the results of theoretical and experimental studies of heterostructure insulated-gate field-effect transistors (HIG' FET's). We develop an improved charge-control model for the two-dimensional densities of electronand hole gases at the heterointerface. Our model provides an accurate description of the device behavior even at relatively low densities of two-dimensional gases. We obtain the current-voltage characteristics of HIGFET's using our charge-control model and account for the gate current. The theoretical calculations are in good agreement with the experimental measurements.

New mechanism of gate current in heterostructure insulated gate field-effect transistors

We demonstrate that the mechanism responsible for the gate current in heterostructure insulated gate field-effect transistors (HIGFET's) changes drastically at the gate voltage equal to the threshold voltage. At the gate voltages below the threshold voltage the gate current is determined by the thermionic emission over the Schottky barrier at high temperatures and by the thermionic field emission at low temperatures. Above the threshold the gate current is determined by the new mechanism which is the thermionic emission over the conduction band discontinuity at high temperatures and by tunneling through the AlGaAs layer at low temperatures. We present the model describing the gate current in the entire range of the gate voltages and device temperatures.