Abstract
An optically activated, enhancement mode heterostructure field effect transistor is proposed and analytically studied. A particular feature of this device is its gate region, which is made of a photovoltaic GaN/AlN-based superlattice detector for a wavelength of 1.55 µm. Since the inter-subband transition in this superlattice does normally not interact with TE-polarized (or vertically incoming) radiation, a metallic second-order diffraction grating on the transistor gate results in a re-orientation of the light into the horizontal direction—thus providing the desired TM-polarization. Upon illumination of this gate, efficient inter-subband absorption lifts electrons from the ground to the first excited quantized state. Due to partial screening of the strong internal polarization fields between GaN quantum wells and AlN barriers, this slightly diagonal transition generates an optical rectification voltage. Added to a constant electrical bias, this optically produced gate voltage leads to a noticeable increase of the transistor’s source-drain current. The magnitude of the bias voltage is chosen to result in maximal transconductance. Since such a phototransistor based on high-bandgap material is a device involving only fast majority carriers, very low dark and leakage currents are expected. The most important advantage of such a device, however, is the expected switching speed and, hence, its predicted use as an optical logic gate for photonic computing. In the absence of a p-n-junction and thus of both a carrier-induced space charge region, and the parasitic capacitances resulting thereof, operation frequencies of appropriately designed, sufficiently small phototransistors reaching 100 GHz are envisaged.
Highlights
Semiconductor-based transistors have been invented and first demonstrated by J.Bardeen and W.H
We, present the design and simulation of a GaN/AlN-based, rugged and fast phototransistor with a 1.55 μm inter-subband detector acting on the transistor gate
In order to pave the way for a practical realization of these propositions, we present here a simple model which predicts correct device operation at modulation frequencies of up to 100 GHz
Summary
Semiconductor-based transistors have been invented and first demonstrated by J. We, present the design and simulation of a GaN/AlN-based, rugged and fast phototransistor with a 1.55 μm inter-subband detector acting on the transistor gate. In this type of device, the absence of a p-n-junction, of a space charge region, lifts one big, omnipresent problem of bipolar transistors: In terms of limiting frequency, bipolar devices always hit a ‘hard stop’ defined by their parasitic capacitance. As a fourth and probably most important measure, the presented superlattice (SL) detector will become the gate region of a monolithically integrated, normally-off HFET [12] This strategy will boost the existing signal size to a usefully large value. In order to pave the way for a practical realization of these propositions, we present here a simple model which predicts correct device operation at modulation frequencies of up to 100 GHz
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
