LARGE-BAND-GAP SIC, III-V NITRIDE, AND II-VI ZNSE-BASED SEMICONDUCTOR-DEVICE TECHNOLOGIES

In the past several years, research in each of the wide-band-gap semic onductors, SiC, GaN, and ZnSe, has led to major advances which now mak e them viable for device applications. The merits of each contender fo r high-temperature electronics and short-wavelength optical applicatio ns are compared. The outstanding thermal and chemical stability of SiC and GaN should enable them to operate at high temperatures and in hos tile environments, and also make them attractive for high-power operat ion. The present advanced stage of development of SiC substrates and m etal-oxide-semiconductor technology makes SiC the leading contender fo r high-temperature and high-power applications if ohmic contacts and i nterface-state densities can be further improved. GaN, despite fundame ntally superior electronic properties and better ohmic contact resista nces, must overcome the lack of an ideal substrate material and a rela tively advanced SiC infrastructure in order to compete in electronics applications. Prototype transistors have been fabricated from both SiC and GaN, and the microwave characteristics and high-temperature perfo rmance of SiC transistors have been studied. For optical emitters and detectors, ZnSe, SiC, and GaN all have demonstrated operation in the g reen, blue, or ultraviolet (UV) spectra. Blue SiC light-emitting diode s (LEDs) have been on the market for several years, joined recently by UV and blue GaN-based LEDs. These products should find wide use in fu ll color display and other technologies. Promising prototype UV photod etectors have been fabricated from both SiC and GaN. In laser developm ent, ZnSe leads the way with more sophisticated designs having further improved performance being rapidly demonstrated. If the low damage th reshold of ZnSe continues to limit practical laser applications, GaN a ppears poised to become the semiconductor of choice for short-waveleng th lasers in optical memory and other applications. For further develo pment of these materials to be realized, doping densities (especially p type) and ohmic contact technologies have to be improved. Economies of scale need to be realized through the development of larger SiC sub strates. Improved substrate materials, ideally GaN itself, need to be aggressively pursued to further develop the GaN-based material system and enable the fabrication of lasers. ZnSe material quality is already outstanding and now researchers must focus their attention on address ing the short lifetimes of ZnSe-based lasers to determine whether the material is sufficiently durable for practical laser applications. The problems related to these three wide-band-gap semiconductor systems h ave moved away from materials science toward the device arena, where t heir technological development can rapidly be brought to maturity.