Current status of wide bandgap (WBG) semiconductor material technology is evaluated for developing high-performance and reliable power electronics switching converters. The study takes into account field reliability of silicon power metal-oxide-semiconductor field-effect transistors (MOSFETs) in compact computer/telecom power supplies where residual material defects present in the silicon space-charge region were found to generate local microplasma that eventually caused power MOSFETs to fail under long-term repetitive field-switching conditions. It is shown that silicon power MOSFETs with increased low-level leakage currents are more prone to field failures in high-density power supplies. A new single-event burnout (SEB) stress testing methodology is proposed; the SEB stress test results are shown to correlate well with silicon power MOSFET failures in power supply circuits. Based on these results and the current state of the art of silicon carbide (SiC) and gallium nitride (GaN) power devices, a “reliability-driven” manufacturing approach is recommended for rapid commercialization and market penetration of WBG semiconductor power devices.

Metal-organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) are the principal techniques for the growth and n-type (Si) and p-type (Mg) doping of III-nitride thin films on sapphire and silicon carbide substrates as well as previously grown GaN films. Lateral and pendeoepitaxy via MOVPE reduce significantly the dislocation density and residual strain in GaN and AlGaN films. However tilt and coalescence boundaries are produced in the laterally growing material. Very high electron mobilities in the nitrides have been realized in radio-frequency plasma-assisted MBE GaN films and in two-dimensional electron gases in the AlGaN/GaN system grown on MOVPE-derived GaN substrates at the crossover from the intermediate growth regime to the droplet regime. State-of-the-art Mg doping profiles and transport properties have been achieved in MBE-derived p-type GaN. The Mg-memory effect, and heterogeneous growth, substrate uniformity, and flux control are significant challenges for MOVPE and MBE, respectively. Photoluminescence (PL) of MOVPE-derived unintentionally doped (UID) heteroepitaxial GaN films show sharp lines near 3.478 eV due to recombination processes associated with the annihilation of free-excitons (FEs) and excitons bound to a neutral shallow donor (D/spl deg/X).

Recent developments in III-V nitride thin-film materials for electronic and optoelectronic applications are reviewed. The problems that are limiting the development of these materials and devices made from them are discussed. The properties of cubic boron nitride, aluminum nitride, gallium nitride, AlN/GaN solid solutions and heterostructures, and indium nitride are discussed. It is pointed out that the lack of a suitable substrate, with the possible exception of SiC for AlN, is a problem of considerable magnitude. This is compounded by the presence of shallow donor bands in GaN and InN which are apparently caused by N vacancies. The question of whether these vacancies occur (if they do) as a result of intrinsic or extrinsic (as a result of deposition) nonstoichiometry has not been answered. However, the recent advances in the fabrication of p-type GaN and a p-n junction light emitting diode via the electron beam stimulation of the Mg dopant are very encouraging and may considerably advance the technology of this material. This would indicate that self-compensation effects, similar to those observed in ZnO and ZnSe, may not be present in the III-V nitrides, since cubic BN (cBN) AlN and now GaN have been reportedly doped both n- and p-type.>

The deposition of silicon carbide thin films and the associated technologies of impurity incorporation, etching, surface chemistry, and electrical contacts for fabrication of solid-state devices capable of operation at temperatures to 925 K are addressed. The results of several research programs in the United States, Japan and the Soviet Union, and the remaining challenges related to the development of silicon carbide for microelectronics are presented and discussed. It is concluded that the combination of alpha -SiC on alpha -SiC appears especially viable for device fabrication. In addition, considerable progress in the understanding of the surface science, ohmic and Schottky contacts, and dry etching have recently been made. The combination of these advances has allowed continual improvement in Schottky diode p-n junction, MESFET, MOSFET, HBT, and LED devices.>