Sensitivity of N-polar GaN surface barrier to ambient gases

Abstract Modulation spectroscopy was applied to study the N-polar GaN surface barrier height dependency on ambient gas type in GaN/GaN:Si and GaN/AlGaN/GaN heterostructures. The built-in electric field in the undoped layer of the GaN/GaN:Si structure was determined by an analysis of a Franz-Keldysh oscillation present in spectra and used to calculate the surface barrier in presence of various gases. A barrier of 0.35 eV in air and N 2 +O 2 (82:18 ratio) mixture ambient was determined while in vacuum, N 2 , Ar and SF 6 it amounted to 0.20 eV. No effect of humidity on the surface barrier was observed. The GaN channel built-in electric field of the GaN/AlGaN/GaN heterostructure was also determined from optical studies. It was then used as a parameter in a self-consistent solution of Schrodinger-Poisson equations in order to calculate the surface barrier for this structure in air and vacuum ambient, and the results matched those obtained for the UN + structure. This indicated that the electronic state of surface behaves in the same way irrespectively of the structure design. Calculated carrier concentration of the GaN/AlGaN/GaN heterostructure shows a significant dependency on the surface barrier indicating a possible application in gas sensing. The response time was also studied showing a fast (