Improving thermal stability of InGaN quantum wells by doping of GaN barrier layers

Abstract

Thermal instability of InxGa1−x N quantum wells (QWs) is an obstacle to construct efficient blue and green LEDs and laser diodes. Structural degradation of QWs with indium content above 15% becomes severe at temperatures above 930 °C leading to formation of extended non-radiative areas within the active region. Our previous studies (Smalc-Koziorowska, 2021) indicated a relationship between the degradation process and metal vacancies present in the layers adjacent to the QWs. In this work, we show a method to overcome this problem by using heavy Si doping of the GaN barrier layers. In particular, such barrier layer grown on the top of n-type GaN layer below the InGaN QWs can act as a diffusion barrier for vacancies. The presence of silicon atoms increases the energy barrier for gallium vacancies migration. This effectively reduces possibility of diffusion of gallium vacancies from the n-type layer to the active region. As a result, improved thermal stability of QWs was achieved and significant degradation was not observed up to temperatures of 980 °C in comparison to 930 °C for the undoped structure.