AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS+EM+SC-ThA

Paper SS+EM+SC-ThA8
Thermal Desorption of Deuterium from GaN(0001): A Sensitive Probe of Surface Preparation

Thursday, November 18, 2004, 4:20 pm, Room 210C

Session: Compound Semiconductor Growth and Surface Structure
Presenter: C.M. Byrd, Naval Research Laboratory
Authors: C.M. Byrd, Naval Research Laboratory
J.N. Russell, Jr., Naval Research Laboratory
Correspondent: Click to Email
Gallium nitride (GaN) is a wide band gap semiconductor with applications in high temperature, power and frequency optoelectronic devices. The surface chemistry of hydrogen on GaN affects growth rates and electronic passivation, while annealing temperatures impact both ohmic contacts and thermal stability. In this work, the preparation of a GaN(0001) thin film surface was investigated as a function of anneal temperature (300-1100K) using Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), low energy electron diffraction (LEED), and temperature programmed desorption (TPD). After the GaN(0001) surface was sputter cleaned with nitrogen (N@sub 2@@super +@) ions, N@sub 2@ desorption was observed at 950 K from embedded nitrogen and then above 1200 K from GaN decomposition. EELS and AES showed subtle changes as the anneal temperature increased, and the LEED pattern sharpened. TPD spectra were collected for a series of anneal temperatures. After annealing the surface and cooling to room temperature, the surface was dosed with D atoms. When heated at 1 K/s, D@sub 2@ thermal desorption was observed, but not ammonia or gallane. There were four D@sub 2@ thermal desorption peaks at 430, 600, 730 and 810 K, the appearance and relative intensities of which were related to whether the anneal occurred at, above, or below the embedded nitrogen desorption temperature. Correlation of the anneal temperature dependence of the D@sub 2@ thermal desorption with the EELS, AES, and LEED data aided in identifying the origins of the D@sub 2@ desorption states. This work demonstrates D@sub 2@ thermal desorption is very sensitive to the quality of the GaN(0001), and explains differences in hydrogen on GaN(0001) TPD results in the literature.