TITLE: GaN based modulation doped, quantum well, and quantum dot heterostructures

SPEAKER: Professor Hadis Morkoç,

GaN and related materials exhibit optical and transport characteristics that are very well suited for visible opto-electronic devices and electronic devices (relying on electron transport). This is evident by successful LEDs, lasers, detectors, and the recent high power MODFETs with record power performance, which supplanted all the other competing semiconductors at microwave frequencies. Recent theoretical and experimental investigations indicate that polarization induced charge is important in nitride semiconductors and heterostructures with device implications and that spontaneous polarization is sizeable in many cases over the strain induced piezoelectric polarization in typical GaN/AlGaN structures. However, the differential spontaneous polarization between GaN and InN is much smaller than that of GaN/AlN interfaces. Full or partial relaxation of InGaN on GaN due to defects and inhomogeneities such as compositional fluctuations would reduce this piezoelectric polarization further. Another exciting development is recent emergence of quantum dot-like GaN structures. In this presentation motivation for, preparation and properties of GaN/AlGaN heterostructures along with pertinent polarization effects will be presented.