Current–voltage characteristics of polar heterostructure junctions

We report calculations that show that a metal–polar semiconductor heterostructure can exhibit highly controllable nonlinear current–voltage characteristics. A change in barrier thickness can alter the characteristics from Schottky-like to ohmic in different bias regimes. The origin of these unusual effects is a large electric field (>106 V/cm)(>106 V/cm) and high sheet charge(∼1013–1014cm−2)(∼1013–1014cm−2) without doping, in the polar heterostructure. Theoretical calculation of the tunneling current density in these systems is done in this work. The results indicate that very interesting nonlinear behavior is shown by these systems, even in the undoped case. The choice of suitable compositions of the materials and thicknesses can be used to tailor devices with desired characteristics. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71184/2/JAPIAU-91-5-2989-1.pd

Fabrication of single or multiple gate field plates

"This invention relates to semiconductor devices, and more particularly, to the fabrication of single or multiple gate field plates.

Examination of tunnel junctions in the AlGaN/GaN system: Consequences of polarization charge

A strong piezoelectric effect and a large spontaneous polarization allow one to incorporate a large electric field (>106 V/cm)(>106V/cm) and high sheet charge (>1013 cm−2)(>1013cm−2) without doping in the AlGaN/GaN heterostructure. Theoretical studies are done to examine how polarization effects can be exploited to design metal–AlGaN/GaN tunnel junctions. We find that with a proper choice of AlGaN thickness undoped junctions can be made with very high metal to two-dimensional electron gas tunneling. Thus, a Schottky junction can be converted to a tunnel junction without doping. The tunneling probabilities approach those produced in a system doped at ∼ 4×1019 cm−3.∼4×1019cm−3. This work suggests that very interesting tunnel junctions can be made from undoped AlGaN/GaN heterostructures. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70932/2/APPLAB-77-12-1867-1.pd

Study of charge control and gate tunneling in a ferroelectric-oxide-silicon field effect transistor: Comparison with a conventional metal-oxide-silicon structure

It is known that conventional metal-oxide-silicon (MOS) devices will have gate tunneling related problems at very thin oxide thicknesses. Various high-dielectric-constant materials are being examined to suppress the gate currents. In this article we present theoretical results of a charge control and gate tunneling model for a ferroelectric-oxide-silicon field effect transistor and compare them to results for a conventional MOS device. The potential of high polarization charge to induce inversion without doping and high dielectric constant to suppress tunneling current is explored. The model is based on a self-consistent solution of the quantum problem and includes the ferroelectric hysteresis response self-consistently. We show that the polarization charge associated with ferroelectrics can allow greater controllability of the inversion layer charge density. Also the high dielectric constant of ferroelectrics results in greatly suppressed gate current. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71117/2/JAPIAU-89-3-1856-1.pd

Influence of active layer thickness on electrical properties of P3HT/n-Si based hybrid heterostructure

In the present study, we analyze the effect of active (organic) layer thickness on the optical and electrical properties of poly 3-hexylthiophene/n-silicon hybrid hetero-structure. The organic/inorganic sandwiched heterojunction have been prepared via spin-coating of poly 3-hexylthiophene film onto an oxide passivated Si substrate at room temperature. The device structure has been fabricated via depositing silver and aluminum contacts on Poly 3-hexylthiophene and n-silicon layers, respectively. The optical and electrical properties of the fabricated heterostructures have been examined by varying the active layer thickness from 50 to 120 nm. Photoluminescence measurements displayed a sharp intense peak at 578 nm corresponding to characteristic poly 3-hexylthiophene band-to-band transition. Enhancement in forward current and reduction in leakage current was observed with increased active layer thickness. It has been observed that employing an active layer thickness of 100 nm, the device produces enhanced forward currents with low leakage currents which leads to the formation of high quality heterojunction and demonstrates better performance of the device