The surface recombination velocity in n-type heteroepitaxial GaN(0001) is shown to decrease dramatically when the surface is chemically treated with aqueous and alcoholic solutions of inorganic sulfides, such as ammonium or sodium sulfide ((NH4)2Sx and Na2S). The room-temperature excitonic photoluminescence (PL) intensity increases by a factor of four to six after treatment, and improvements persist for at least seven months in room air. Various other chemicals commonly used in device processing are investigated and shown to change the PL intensity by factors ranging from 0.7 to 2.5, buffered oxide etching being the most beneficial. Schottky barrier diodes using gold as the contact metal are fabricated using a sulfide treatment prior to evaporation. The barrier height from capacitance-voltage measurements is as high as 1.63±0.07 V, the highest value ever achieved on n-GaN. This result is evidence that the effect of surface states on the Fermi level has been substantially reduced by the treatment.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry