Fabrication of InGaN quantum dots by periodically interrupted growth in MOCVD

Abstract

Self-assembled InGaN quantum dots are fabricated in a two-flow horizontal MOCVD reactor maintained at the pressure of 200 torr. The precursors were trimethyl-gallium (TMG) and trimethyl-indium (TMI) and ammonia (NH₃), and the carrier gas was N₂ and H₂. The optimum condition for periodically interrupted growth (PIG) mode was deduced to fabricate the InGaN quantum dots. NH₃ was supplied in PIG mode with the interval of 3 seconds and 5 seconds while TMG and TMI were supplied continuously. The carrier gas was N₂ in QDs growth, while H₂ in nucleation and buffer layer growth. The influence of number of periodic interrupted NH₃ on the structural and optical properties of InGaN quantum dots was investigated by AFM, FE-SEM and low temperature photoluminescence (LT-PL). The AFM images give the size of InGaN QDs with diameter of 20 ~ 50 nm, height of 3 ~ 10 nm and density of 10¹⁰ #/cm² ~ 10¹¹ #/cm². A strong peak at 362.2 nm (3.41eV) and broad emission peak in 435 nm (2.86 eV) were evolved in the photoluminescence measurement using Nd-YAG laser. The composition of QDs was estimated to be In_0.14Ga_0.86N from the relation between peak energy and indium content. Hence. The periodic interruption growth enables the fabrication of self- assembled InGaN QDs with high density and uniform size.