Novel Physics and Applications of InN

The objective of this investigation is to explore the novel characteristics of InN compound semiconductors and their application. Room temperature metallic behaviour and superconductivity of wurtzite-structured (WZ)InN thin films have been discovered in our previous study recently.Because superconductivity in degenerate semiconductors is an interesting issue for both theory and experiment. Such carrier density dependence of Tc has been reported for heavily boron-doped diamond thin films and was explained in the framework of electron-phonon coupling of the same type as in MgB2, but in three dimensions. The coupling strength is as function of hole-doping. The superconductivity is type II and isotropic. This is quite different from naturally n-type InN. The mechanism of superconductivity in unintentionally doped n-type InN remains unclear. Despite the intense study was mad, experimental investigations of superconducting mixed state properties in InN system are minuscule. Mechanism of Superconducting and anomalous mixed-state behavior observed in this system have not been realized yet. A research program on high quality InN thin film, p-type InN, as well as other heavily doped semiconductors and their applications is proposed. It combines various novel properties of InN to fabricate Schotky barriers, p-n junctions and solar cells. The proposal includes (1) Growth of high quality InN thin film on sapphire with changing V/III ratios, temperatures and buffer layers. (2) To make InGaN, p-type InN and heavily doped semiconductors by varying MOCVD growth along with other techniques. (3) Study of InN series and heavily doped semiconductors for their superconductivity and the effect of doped concentration. (4) To make schottky barriers and p-n junctions using undoped and doped InN. (5) Establishment of a general rule to couple semiconductors with superconductors. Being direct bandgap semiconductors, this material suffers from the lack of a suitable substrate and large disparity of the atomic radii of In and N, which cause high native defect concentrations in it. The native defect responsible for naturally occurring n-type InN is nitrogen vacancy The resistance is metallic like over a wide temperature range (4 K . T . 300 K) and R (300K) / R (4K) is about 1.1. The carrier concentration and mobility measurements show the InN thin films in this range a degenerate electronics system. Anomalous Hall effects were observed at 0.3 K. The potential of using InN for the high mobility electronics and a wide range of optoelectronic devices, such as laser diode丟light-emitting diodes丟solar cells丟IR detectors 丟THz emitters, has not been explored because the p-type InN has not been successfully grown to date. It is due to its position of the conduction band edge at 0.9 eV below EFS. More recently, R. E. Jones et al. have shown that InN:Mg films consist of a p-type bulk region with a thin n-type inversion layer at the surface that prevents electrical contact to the bulk. In this project, we are trying to reduce the intrinsic background concentration of InN and perform C-V-T, I-V measurement by fabrication InN/GaN Schottky barriers.We hope to realize the p-doping in InN. After p-InN becomes realized, InN p-n junction will be possible. It will be very interesting to study the InN-based solar cell grown by MOCVD.We will cooperate with Professor M.K.Wu and D.C.Lin and I.K.Chen in the investigation of novel superconductivity (SC) of InN, and Professor C.C.Chi in the nano-scale SC properties of InGaN by Scanning SQUID Microscope (SSM). In the study of optical (XRD and Raman), we will work with Professor H.L. Liu and Professor C. H. Du. Our capabilities include (1) MOCVD Growth of high quality InN on sapphire and Si with record electron mobility (2).Growth of Mg-doped In1-xGaxN, Al1-xGaxN on sapphire (3) Processing capability of nitride devices. The proposal will be carried out for three years with the following goals: Year One: Epitaxy of high quality InN. The energy bands involved will be modeled, along with the analysis of carrier transport mechanism, superconductivity and magneto-resistance, nanostructure analysis by HRTEM, STM and XRD. The effect of doping concentration on the superconductivity and the effect of nanostructure of InN will also be studied. Year Two: Epitaxy of high quality In1-xGaxN and Mg-doped In1-xGaxN thin films. The effect of Ga and Mg doping on the superconductivity, magneto-resistance and their nanostructure will be explored. The phase separation in the ternary systems and their influence on physical properties will be studied. Year Three: Keep improving the crystal quality of InN and p-type InN. Establishment of a general rule to couple semiconductors with superconductors .Goals for this year include the formation of heavily doped n+GaN and p+Si single crystal thin films by ion irradiation and implanter; realizing the effect of doping concentration on their transport properties as well as superconductivity and nanostructure study; fabrication of n-InN/GaN Schottky barrier, n-InN/p-InN nano junctions and their application to solar cell and LED.

Project ID:PB9706-0887
External Project ID:NSC96-2112-M027-003-MY3