MBE Growth and Characterization of AlGaN/GaN quantum well structures with Large Built-In Electric Fields

Large built-in electric filed have been predicted in the hexagonal III-nitride materials due to spontaneous and piezoelectric. Several groups have studied the effects of these built-in fields on the optical properties of AlGaN/GaN quantum wells. The photoluminescence (PL) peak for wider quantum wells (>30angstroms) has a large red-shift due to the quantum confined Stark effect (QCSE). However, in those studies the AIN mole fraction of the AlGaN barriers were varied only up to about 25%. It is of interest to investigate the magnitude of the built-in electric field with a systematic increase of the AIN mole fraction in the barrier layers and make comparisons to theoretical predictions as these fields play an important role for optical devices. In this work, AlGaN/GaN single and multiple quantum well structures have been grown on (0001) sapphire substrates by molecular beam epitaxy.