Fabrication and Optical Recombination in III-Nitride Microstructures and Devices

The research program at Kansas State University is to develop innovative approaches for fabricating high quality III- nitride QWs, heterostructures, microstructures, and micro-devices and to study their optical and optoelectronic properties. By optimizing the epilayer mobilities and optical emission properties, we have produced GaN,Al(x)Ga(1-x)N (x up to 1), In(x)Ga(1-x)N (x<0.3), and In(x)Al( y)Ga(1-x-y)N epilayers, III-nitride QWs with device qualities. We have successfully fabricated micro-size blue emitters and developed a bonding scheme that allows us to address micro-size pixels individually in an array comprising many 111-nitride micro-emitters/micro-detectors. We have demonstrated the operation of the first prototype blue microdisplay made from InGaN/GaN QWs. We have achieved highly conductive n-type Al(x)Ga(1-x)N alloys of high Al contents (for x up to 0.8). We have developed Mg-delta-doping for enhanced p-type doping efficiency in GaN and AlGaN. A 2-fold enhancement in lateral and a 5-fold enhancement in vertical p-type conductions have been achieved for AlGaN and AlGaN epilayers. We have also achieved AlN epilayers with very efficient band-edge PL emission the optical quality of AlN is comparable to that of GaN and determined the detailed band structure near the gamma point of wurtzite AlN, including energy gap, optical selection rules, exciton binding energies and lifetimes, and acceptor/donor energy levels.
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