Molecular beam epitaxy growth and properties of GaN, InGaN, and GaN/InGaN quantum well structures

Abstract

Growth of III–V nitrides by molecular beam epitaxy (MBE) was studied using rf nitrogen plasma sources. Plasma sources from three different vendors have been tested. All three of the sources have been used to grow high quality GaN. However, the EPI rf source produces an optical emission spectrum that is very rich in the active nitrogen species of 1st-positive excited nitrogen molecules and nitrogen atoms. GaN growth rates at 800 °C of 1 μm/h have been achieved using this source. The MBE-grown GaN films are deposited homoepitaxially on high quality metalorganic vapor phase epitaxy-grown GaN/SiC substrates. With the growth conditions for high quality undoped GaN as a base line, a detailed study of Mg doping for p-type GaN was performed. An acceptor incorporation of 2×1019 cm−3 was measured by both capacitance–voltage and secondary ion mass spectroscopy for a doping source temperature of 290 °C. However, a faceted three-dimensional growth mode was observed by reflection high energy electron diffraction during Mg doping of GaN. Additional studies suggest an interdependence between Mg incorporation and growth surface morphology. Quantum well structures made from the InGaN ternary alloy were grown using a modulated beam MBE method. With this technique, quantum well compositions were controllable, grown with visible luminescence ranging from 400 to 515 nm depending on indium mole fraction. Light emitting diode test structures, combining Mg p-type doping with InGaN quantum wells, were fabricated and tested.