Selective layer disordering in intersubband Al_0.028Ga_0.972N/AlN superlattices with silicon nitride capping layer

Abstract

Selective layer disordering in an intersubband Al 0.028 Ga 0.972 N/AlN superlattice using a silicon nitride (SiN x ) capping layer is demonstrated. The SiN x capped superlattice exhibits suppressed layer disordering under high-temperature annealing. Additionally, the rate of layer disordering is reduced with increased SiN x thickness. The layer disordering is caused by Si diffusion, and the SiN x layer inhibits vacancy formation at the crystal surface and ultimately, the movement of Al and Ga atoms across the heterointerfaces. Patterning of the SiN x layer results in selective layer disordering, an attractive method to integrate active and passive III-nitride-based intersubband devices.

Interdiffusion of Al and Ga in AlN/AlGaN superlattices grown by ammonia-assisted molecular beam epitaxy

“…Chemical diffusion is another well-known phenomenon that can lead to an interface layer. So far few studies have dealt with cation interdiffusion in the GaN/AlN system: during MOCVD growth at 1100 °C [7] and after annealing at temperatures going from 1000 °C to 1700 °C [8][9][10]. Based on these studies a set of diffusion coefficients were reported in the literature, but the estimated values spread over a wide range and are not consistent with each other, even if their temperature dependence is taken into account.…”

“…Based on these studies a set of diffusion coefficients were reported in the literature, but the estimated values spread over a wide range and are not consistent with each other, even if their temperature dependence is taken into account. In Al0.03Ga0.97N/AlN superlattices (SLs) a D value of 7⨯10 -20 cm 2 /s has been reported at 1000 °C [8] and a D value of 1.3⨯10 -17 cm 2 /s has been extracted from experiments in Al0.06Ga0.94N/GaN quantum well structures annealed at 1500 °C [9]. While a D value as high as 10 -14 cm 2 /s has been determined for Al0.02Ga0.98N/GaN and AlN/GaN structures annealed at 1100 °C [7].…”