Accession Number : ADA322688

Title :   Metalorganic Chemical Vapor Deposition of GaN, AlN, and GaAlN for UV Photodetector Applications. Development of III-Nitride Technology for Optoelectronic Devices.

Descriptive Note : Annual rept. Apr 96-Mar 97,

Corporate Author : NORTHWESTERN UNIV EVANSTON IL

Personal Author(s) : Razaghi, Manijeh

PDF Url : ADA322688

Report Date : 06 MAR 1997

Pagination or Media Count : 71

Abstract : The cause of the X-ray diffraction peak broadening in GaN epilayers grown on sapphire (Al2O3) substrates was investigated and attributed to a limited in-plane coherence length. Screw and mixed dislocation densities less than ^10(exp 7) /sq cm were achieved in GaN epilayers on Al2O3. On the same Al2O3 wafer, up to two inches in diameter, GaN films exhibited mirror-like surface morphologies, good uniformity, narrow X-ray diffraction (30 arcsecs) and narrow bandedge photoluminescence emission lines (17 meV at 77K). The n-type and p-type doping control of GaN were improved (n up to ^10(exp 20) /cu cm and mu-n increased to >300 sq cm/Vs, while p increased up to 3x10(exp 17) /cu cm at 300K). The quality of Al(x)Ga(1-x)N films on Al2O3 (0<=x<=1) was improved. The (00.2) X-ray diffraction linewidths were <4 arcmins. The n-type and p-type doping control of Al(x)Ga(1-x)N were achieved up to Al concentrations of 50% and 30%, respectively. Al(x)Ga(1-x)N-based Bragg reflectors, two dimensional electron gas structures, Al(x)GA(1-x)N/GaN superlattices exhibiting clear X-ray diffraction satellite peaks (up to the 10th peak) were demonstrated. The atomic sharpness of the interfaces was confirmed through cross-sectional transmission electron microscopy. Monocrystalline GaN was grown on quasi lattice-matched Beta-LiGaO2 substrates by MOCVD, with X-ray diffraction linewidths of 300 arcsecs and intense near bandedge photoluminescence. Al(x)Ga(1-x)N-based ultraviolet photoconductors were achieved with cut-off wavelengths from 365 to 200 nm. Detectivities D# were measured to be ^10(exp 9) cm-Hz(1/2)/W. After the dry etching system was installed, GaN p-i-n mesa structures were fabricated. The response speed of these photodiodes was significantly increased and was limited by the circuit RC time constant.

Descriptors :   *ALUMINUM COMPOUNDS, *ULTRAVIOLET RADIATION, *CHEMICAL VAPOR DEPOSITION, *NITRIDES, *PHOTODETECTORS, *GALLIUM COMPOUNDS, VELOCITY, DENSITY, ELECTROOPTICS, LAYERS, PHOTOLUMINESCENCE, SUPERLATTICES, X RAY DIFFRACTION, EMISSION SPECTRA, ORGANOMETALLIC COMPOUNDS, SUBSTRATES, ETCHING, ELECTRON MICROSCOPY, TRANSMITTANCE, SAPPHIRE, DISLOCATIONS, CROSS SECTIONS, MIXING, DOPING, CIRCUITS, DRY MATERIALS, PHOTODIODES, P TYPE SEMICONDUCTORS.

Subject Categories : Inorganic Chemistry
      Organic Chemistry
      Physical Chemistry
      Electrooptical and Optoelectronic Devices

Distribution Statement : APPROVED FOR PUBLIC RELEASE