Improving the growth of pulsed chemical vapor deposition of GaN on Si(100) by <i>in situ</i> ammonia nitriding of the Si surface

Abstract

The morphology, crystallinity, and photoconductive properties of gallium nitride films grown by pulsed chemical vapor deposition on p-type Si(100) with and without ammonia (NH3) pretreatment are investigated. Ammonia pretreatments were performed at 525 °C and 800 °C, which resulted in GaN film thicknesses of 80 and 140 nm, respectively. An amorphous film of GaN is obtained without pretreatment and a polycrystalline GaN film with pretreatment. X-ray photoelectron spectroscopy showed that the pretreatment results in a 1–2 nm bilayer consisting of SiNx and SiOxNy at the GaN/Si interface. Photoconductive measurements show the 525 °C pretreated GaN film has a responsivity of 72 mA W−1 and a rise time of 0.37 ms, whereas the GaN film with an 800 °C pretreatment has a responsivity of 246 mA W−1 and a rise time of 1.7 ms. Moreover, the photocurrent of the 525 °C pretreated device exhibits superlinear power dependence with a power coefficient of 1.74, whereas the 800 °C pretreated device exhibits sublinear power dependence with a power coefficient of 0.58. The superlinear power dependence of the photoresponse of the 525 °C pretreated film is attributed to the presence of fast and slow recombination centers.