EPITAXIAL FILM BAND GAP/COMPOSITION MAPPING USING ELECTRON BEAM ELECTROREFLECTANCE: OPTICAL CHARACTERIZATION OF HIGH X ALGAAS WAFERS

IN PHASE I, WE PROPOSE TO INVESTIGATE THE USE OF ELECTRON BEAM ELECTRO-REFLECTANCE (EBER) TO AUTOMATICALLY MAP THE BAND GAP OF HIGH X ALGAAS (X>0.38) EPITAXIAL FILMS ON FULL, 3 INCH GAAS SUBSTRATES AT ROOM TEMPERATURE. THESE COMPOSITIONS OF ALGAAS ARE IMPORTANT FOR HIGH-EFFICIENCY GRINSCH LASERS AND OTHER APPLICATIONS, BUT AS THE CRYSTAL SWITCHES TO AN INDIRECT GAP ABOVE THIS X VALUE, TRADITIONAL OPTICAL METHODS SUCH AS PHOTOLUMINESCENCE (PL) FAIL. WE HAVE ALREADY BEEN SHOWN THAT HIGH X AL(X)GA(1-X)AS FILMS MAY BE SUCCESSFULLY TESTED BY EBER DURING EARLIER RESEARCH. THIS PHASE I WORK WILL INVESTIGATE THE APPLICABILITY OF EBER TO WAFER-SCALE ANALYSIS AND MAPPING OF THESE HIGH X FILMS. FOR THIS PURPOSE, WE WILL MEASURE THE E(0) AND E(1) FEATURES OF BOTH THICK (SEVERAL MICRONS) AND THIN (0.1 MICRON) MBE GROWN AL(X)GA(1-X)AS FILMS OF NOMINAL X = 0.5, 0.6, 0.7, AND 0.8. OUR OBJECTIVE IS TO OBSERVE AND PARAMETRIZE THE OPTICAL MODULATED REFLECTANCE FEATURES OF ALGAAS FILMS IN THE INDIRECT-GAP REGIME.