혼합소스 HVPE 법에 의한 InGaN 나노구조 성장에 관한 연구

Abstract

InGaN alloys are important for the development of optical devices because the band-gap energy of wurzite GaN and InN are 3.4 eV and 0.7 eV, respectively. However, as a result of thermodynamic limit and high InN vapor pressure, it is difficult to grow high quality InxGa1-xN with high indium composition. Especially, InGaN structure which is in nano or micro size is expected to show great deal of application use because of its decrease in density of states, dislocation density and relaxation of strain as well as increase of carrier confinement.

We studied the effect of the type of substrate on the growth of InGaN nanostructures by mixed-source hydride vapor phase epitaxy (HVPE). InGaN nanostructures were formed on c-plane, r-plane sapphire, and undoped GaN substrates at various growth temperatures. Also, we looked into the changes in the structural and optical characteristics of InGaN nanostructures when antimony (Sb) is used as a surfactant during the growth of InGaN nanostructures. The samples were characterized by scanning electron microscopy (SEM) and photoluminescence (PL) measurement. The density of the nanostructures and the indium composition of the InGaN layer varied depending on the growth temperature. InGaN nanostructures grown without Sb were preferentially oriented in the c-axis direction with columnar structure while the InGaN nanostructures grown with Sb had random distribution of hexagonal nanostructure on the surface region. From the results of InGaN nanostructures formed with the addition of Sb, we can expect the performance of optical devices would be more improved by reduced piezoelectric field if we use the InGaN nanostructures of which c-axes are aligned parallel to the substrates as an active layer.