This paper presents an analytical model for C-V characteristics of short gate-length GaAs MESFET under illuminated
condition. The non-analytic Gaussian doping profile commonly considered for the channel doping of an ion-implanted
GaAs MESFET has been replaced by an analytic Gaussian-like function for the simplicity of the present model. When
the computed results of the proposed model are compared with numerical simulation data obtained by ATLAS™ device
simulator, an encouraging correspondence between the two lends credibility to our model.
A new optoelectronic integrated device consisting of an n-GaAs optical field-effect transistor (OPFET) and a p-AlGaAs/p-GaAs/n+-AlGaAs surface emitting double heterostructure light emitting diode (DH-LED) which are developed monolithically on a p+-GaAs subtrate and separated by a thin semi-insulating GaAs layer, is proposed in this paper. We call this device as Light Source Integrated-OPFET (LSI-OPFET). The proposed device structure is such that the optical radiation generated by the LED is fed into the OPFET as back illumination. The back radiation is used as the control signal to the OPFET which changes the transconductance of the OPFET. The intensity level of the back illumination to the OPFET can be controlled by changing the bias current of the LED. In this paper, analytical results have been presented for the I-V characteristics and transconductance of the OPFET as a function of the LED current. It has been shown that by changing the level of the back illumination to the OPFET, i.e. by changing the LED current, one can vary both the characteristics and transconductance, which makes the LSI-OPFET as the potential device for the optically controlled varying gain amplifier.
A new optoelectronic integrated device composed of an Optical Field Effect Transistor (OPFET) in series with a double heterojunction light emitting diode (LED) or a laser liode (LD) which can be used as a Light Amplifying Optical Switch (LAOS), is presented in this paper. We shall call this device as OPFET-LAOS since it is a new one in its category. Theoretical investigation has been carried out to develop the I-V characteristic of the proposed device. It is shown theoretically that the device changes its state form a low current (i.e. high impedance) state to a high current (i.e. low impedance) state through a region of negative differential resistance (NDR) when the applied voltage exceeds a certain limit, called the breakover voltage. Thus, the I-V characteristic of the device is similar to that of an existing LAOS composed of a heterojunction phototransistor (HPT) in series with a double heterojunction LED (or LD).