Role of Hydrogen in the CVD of Wide Bandgap Nitride Semiconductors

Abstract

AbstractHydrogen is an important component of the gas‐phase growth chemistry for GaN, which is typically based on NH3 and (CH3)3Ga, and also the processing environment for subsequent device fabrication (e.g., SiH4 for dielectric deposition, NH3 or H2 annealing ambients), and is found to readily permeate heteroepitaxial material at temperatures ≤200 °C. Its main effect has been the passivation of Mg acceptors in p‐GaN through the formation of neutral Mg‐H complexes, which can be dissociated through minority‐carrier (electron) injection or simple thermal annealing. Atomic hydrogen is also found to passivate a variety of other species in GaN, as detected by a change in the electrical or optical properties of the material. The injection of hydrogen during a large variety of device fabrication steps has been detected by secondary ion mass sprectrometry (SIMS) profiling using 2H isotopic labeling. Basically all of the acceptor species in GaN, i.e., Mg, C, Ca, and Cd, are found to form complexes with hydrogen.