Metal-semiconductor Heterojunction Research Articles

Solid-state electric generator based on chemically induced internal electron emission in metal-semiconductor heterojunction nanostructures

Internal electron emission induced by hydrogen oxidation to water on surface of Pd/n-SiC heterojunction nanostructures is observed and the possibility for a new type of chemoelectrical power generator is discussed. The noble metal nanolayer serves both as reaction catalyst and emitter of hot electrons traveling over Schottky barrier and toward semiconductor anode. In situ chemical process provides significantly higher output of hot electrons compared to devices with externally heated cathodes. Large fraction of the hot electrons is generated nonadiabatically to complement the usual thermal excitation, leading to very high total internal quantum efficiency of the device, reaching 0.20 for the nanostructure studied here.

Fabrication of Silica‐Shielded Ga–ZnS Metal–Semiconductor Nanowire Heterojunctions

The fabrication of silica shielded Ga-ZnS metal-semiconductor nanowire heterojunction was reported. The fabrication was accompanied with a mixture of ZnS, Ga2O3 and SiO powders as the sources of materials in the vertical induction furnace. A study of the X-ray diffraction pattern shows that the as-synthesized products consists of crystalline zinc-blende form of ZnS. The transmission electron microscopic study shows the microstructural characteristics of the ZnS-based nanostructures.

Metal–semiconductor heterojunctions in T-shaped carbon nanotubes

We report a possible metal–semiconductor carbon nanotube heterojunction which can be done fusing perpendicularly a metallic nanotube to a semiconducting one. Octagonal defects help to make the 90° bend necessary for T-junctions. These molecules could be used as building blocks of nanoelectronic devices.

Influence of PECVD deuterated SiN x on GaAs MESFETs and GaAs/AlGaAs HBTs

The degradation of electrical characteristics of GaAs metal semiconductor field effect transistors (MESFETs) and heterojunction bipolar transistors (HBTs) can occur during plasma enhanced chemical vapor deposition (PECVD) of SiN X passivation films through the hydrogen passivation of dopants or creation of deep traps by ion bombardment or preferential loss of As. In this paper we report in the dc characteristics of MESFETs and HBTs deposited with SiN X using deuterated precursors (SiD 4/ND 3). For the MESFETs, changes in I DS, g m and channel sheet resistance were typically 25%, with process pressure being the most important parameter. For the HBTs, changes in β and sheet resistance of the base and emitter layers were again typically 15% for the conditions we investigated.

Ballistic electron emission microscopy to probe interfaces of simple device structures

Ballistic electron emission microscopy (BEEM) is a powerful new technique capable of probing the electrical barriers at semiconductor interfaces on a microscopic scale. It is also very useful for probing the details of the semiconductor band structures, particularly the positions of the upper valleys in the conduction band. Over the past two years we have used BEEM to investigate both metal-semiconductor contacts and heterojunction interfaces, and we report here some of the data obtained during the investigation. The Au GaAs and Au/InGaAs/AlGaAs systems have been chosen as a vehicle to demonstrate both the power of the technique and its limitations.

A thermodynamic model for determining pressure and temperature effects on the bandgap energies and other properties of some semiconductors

Semiconductor bandgap energies are shown to be equal to the difference between the sum of the standard chemical potentials of free electrons and holes and standard chemical potential of the recombined electron-hole pairs when equilibrium occurs at a given temperature and pressure. The decrease in the bandgap energies of diamond semiconductors with increasing temperature is shown to be caused by the interaction of the free electrons, holes and recombined electron-hole pairs with lattice phonons and linear expansion of the lattice constant. The determined bandgap energies and other intrinsic properties of nondegenerate GaAs are found to be in excellent agreement with experimental data as a function of temperature and pressure. The proposed model is also shown to be useful in determining the effects of temperature and pressure on the intrinsic properties of epilayers and substrate in the metal-semiconductor junctions and heterojunctions.

GaSeGe: A “Schottky-like” heterojunction

Williams et al. recently found, for nonreactive GaSe-metal interfaces, properties similar to those predicted by the Schottky model. We present here evidence that “Schottky-like” properties are also exhibited by the nonreactive interface of the GaSeGe heterojunction. This result emphasizes the link between metal-semiconductor diodes and heterojunctions and opens up the possibility of a unified theory of the built-in potential for nonreactive systems.

High resolution imaging of the interfacial region in metal-insulator-semiconductor and Schottky diodes

Interfacial oxides can greatly influence the properties of metal-semiconductor heterojunctions as demonstrated by recent work on metal-insulator-semiconductor solar cells. The physical structure of such interfacial regions is examined using High Resolution Electron Microscopy. Simultaneous imaging of the lattice structure on both sides of the interfacial region is reported for the first time.

Molecular Beam Epitaxy of III-V Compounds: Application of MBE-Grown Films

The performance of devices fabricated from materials grown by molecular beam epitaxy (MBE) can ideally be used to judge this new film growth technique. From the beginning, microwave and optoelectronic devices have been fabricated from MBE-grown GaAs and AlxGa1_xAs. Initially this work was done mainly at Bell Telephone Laboratories. Fabrication and performance of various devices obtained from MBE material were summarized in excellent reviews by Cho & Arthur (1) and by Cho (2). In the first decade, emphasis was on the MBE production of standard device structures exhibiting characteristics comparable with or even superior to those fabricated by the more conventional growth and processing techniques. Excellent results were obtained for MBE-grown GaAs devices including varactor diodes (3-5), mixer diodes (5, 6-9), IMPATT diodes (10), Gunn diodes (11), MESFETs (12-17), optical waveguides (18-23), and DH injection lasers (24-46). The unique features of MBE have been further applied to more complex device structures involving novel processing steps such as lateral dimensional control as well as metal-semiconductor and oxide-semiconductor heterojunction formation in a single growth cycle. The limits of the MBE technique for the production of novel device structures have not yet been reached.