Accession Number : ADA320478
Title : Interface Properties of Wide Bandgap Semiconductor Structures.
Descriptive Note : Semiannual rept. 1 Jul-31 Dec 96,,
Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
Personal Author(s) : Davis, R. F. ; Bedair, S. ; Bernholc, J. ; Nemanich, R. J. ; Sitar, Z.
PDF Url : ADA320478
Report Date : DEC 1996
Pagination or Media Count : 102
Abstract : Doping of GaN was achieved with doping levels of 5E16 - 3E18 /sq cm. Growth of GaN in H2 and N2 was accomplished with the two main differences being stronger PL intensity and slower growth rate for the films grown in N2. Biaxial strains resulting from mismatches in thermal expansion coefficients and lattice parameters in 22 GaN films grown on AlN buffer layers previously deposited on vicinal and on-axis 6H-SiC(000 1) substrates were measured via changes in the c-axis lattice parameter. A Poisson's ratio of n=0.18 was calculated. The shift in the bound exciton energy with film stress was 23 meV/GPa. As-deposited Pt contacts on Mg-doped, p-type GaN showed ohmic behavior with rc = 0-46 W.cu cm. Values of rc increased upon annealing to a maximum of 8.11x10(exp 3) W.cu cm at 700 deg C due to significant intermixing of Pt, Ga, N, and Mg, as revealed by SIMS analysis. As-deposited, 50 and 100 micrometers dia. Pt Schottky contacts on Si-doped, n-type GaN possessed barrier heights of 1.36 and 1.28 eV, respectively. The ideality factor for both diameters was 1.13. Leakage currents <-1 nA at -10V reverse bias were achieved. A new inductively coupled plasma (ICP) system has been designed, fabricated and initially tested. Parametric studies involving process gas flow rates, ICP and RF bias power and pressure to optimize the system for fast etch rates with the least surface damage/contamination are ongoing. Films of GaN were ion implanted with Si, Mg and Ca/P at energies of 160 keV (Si), 120 keV (Mg), and 180 KeV/130 KeV (Ca/P). The dose varied from 1E14 /sq cm to 1E15 /sq cm for Si and Mg and from 5E14 /sq cm to 5E15 /sq cm for Ca/P. Samples were implanted at 25 deg C (RT) and 550 deg C. Electrical activation has not been observed after repeated annealing. Analysis via RBS showed little or no damage compared to a virgin sample; however no PL spectra were observed in the impla
Descriptors : *PHOTOLUMINESCENCE, *SEMICONDUCTOR DEVICES, COUPLING(INTERACTION), BUFFERS, ACTIVATION, PARAMETRIC ANALYSIS, ENERGY GAPS, CHEMICAL VAPOR DEPOSITION, ION IMPLANTATION, THERMAL EXPANSION, BROADBAND, LATTICE DYNAMICS, DOPING, SCHOTTKY BARRIER DEVICES, TEMPERATURE COEFFICIENTS, POISSON RATIO, ELECTRIC CONTACTS, EXCITONS, RADIOFREQUENCY POWER.
Subject Categories : Solid State Physics
Distribution Statement : APPROVED FOR PUBLIC RELEASE