Growth and Optical Properties of Nonpolar m -plane GaN on Patterned Si and Sapphire Substrates

1. Growth and Optical Properties of Nonpolar m-plane GaN on Patterned Si and Sapphire Substrates Hadis Morkoç, Virginia Commonwealth University, DMR 0907096 Nonpolar and semipolar orientations of GaN are very attractive for optoelectronic applications because they are expected to provide enhanced emission efficiency. In addition to nonpolar m-plane GaN layers on patterned Si(112) substrates, we have investigated the growth habits of semipolar (1-101)-oriented GaN layers and InGaN heterostructures on patterned Si(001) substrates and performed comparitive studies of optical quality of nonpolar and semipolar GaN. Steady-state and time-resolved photoluminescence measurements have revealed that the emission efficiency of semipolar (1-101) GaN is comparable to that of c-plane GaN films grown on sapphire. Slow decay time constants, representative of effective radiative recombination, for semipolar (1-101) GaN were found to be very long, ~1.8 ns, comparable to those for the state-of-art c-plane GaN templates. Studies of p-type doping of m-plane GaN with Mg revealed up to 1019 cm-3 lattice incorporation of Mg and optical properties similar to those of c-plane GaN. Normalized room-temperature time-resolved PL intensity for(1-101) oriented GaN on Si grown at different growth temperatures and c-plane GaN template on sapphire measured at an excitation density of 4 J/cm2. The solid lines represent biexponential fits to the data. The inset shows an SEM image of a (1-101)GaN stripe on 7º offcut patterned Si(100).

2. Growth and Optical Properties of Nonpolar m-plane GaN on Patterned Si and Sapphire Substrates Hadis Morkoç, Virginia Commonwealth University, DMR 0907096 Interaction of students from different universities broadens their perspectives and teaches them the value of collaborative research. By combining spatially resolved CL measurements performed at the Otto-von-Guericke University Magdeburg, Germany (Jürgen Christen) with the growth experiments and optical characterization at VCU, nature of defects and effects of growth parameters on optical performance of nonpolar and semipolar GaN films on Si have been identified. Undergraduate student Christoph Karbaum and graduate student Sebastian Metzner from University Magdeburg, Germany, visited VCU this summer and performed growth and characterization experiments with VCU students. VCU undergraduate student Tyler Selden studied systematically the surfaces of semipolar GaN films to identify the effects of growth conditions on film morphology and strain. Graduate student Sebastian Metznerfrom Otto-von-Guericke University of Magdeburg, Germany, (right) and VCU student Serdal Okur (left) are cooling a CCD detector in preparation for near-field scanning optical microscopy of GaN thin films.