Formation of Ge3N4/Ge Structures Using Nitrogen Radicals and Their Thermal Stability

Abstract

Formation of Ge3N4 on Ge(001) substrates by nitrogen radicals and their thermal stability were investigated in this study. A Ge3N4/Ge structure with a root-mean-square surface roughness of 0.18 nm is successfully formed by layer-by-layer manner at a substrate temperature of 300oC. In contrast, island growth and thermal decomposition of Ge3N4 occur during the nitridation at 600oC, and consequently island structures and locally-flat areas are formed. Ge3N4 thickness is saturated at a certain nitridation time and, not only saturation times but also saturation thicknesses are different depending on plasma condition. By a 2-step nitridation in which the nitridation at 300oC and 600oC for 900 sec were sequentially subjected to Ge surfaces, a Ge3N4 thickness much larger than that at the single-step nitridation can be obtained without surface roughening.