Impurity-induced layer disordering of quantum well heterostructures by silicon diffusion from aluminum-reduced silicon dioxide and silicon nitride

Abstract

In these experiments, impurity-induced layer disordering (IILD) utilizing the chemical reduction of SiO$\sb2$ by Al (from high-percentage Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As) is employed to produce Si and O to effect layer disordering. This diffusion process is examined using secondary ion mass spectroscopy (SIMS) for both closed and open-tube anneal configurations. The thermal stability of strained-layer Al$\sb{\rm y}$Ga$\sb{\rm 1-y}$As-GaAs-In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As quantum well heterostructures is examined using SIMS, transmission electron microscopy (TEM), and photoluminescence (PL) measurements. On samples with acceptable thermal stability, data are presented on both single- and multi-stripe buried heterostructure laser diodes fabricated via Si-O IILD. The stability of a strained-layer In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As quantum well (QW) near critical thickness is examined under high-power, continuous-wave (cw) laser operation in a 10-stripe array fabricated via hydrogenation.

Data are presented describing Si IILD and Al-Ga interdiffusion in Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As-GaAs quantum well heterostructures (QWHs) using an open tube rapid thermal anneal (RTA) furnace (900-1000$\sp\circ$C). The data show that Al-Ga interdiffusion is enhanced by n-type doping and suppressed by p-type doping. By surrounding the active layers of the structure with layers of opposite doping, the data demonstrate that the surrounding layers modify Al-Ga interdiffusion by controlling the diffusion and the solubility of the point defects responsible for layer disordering. The data show that for both n-type and p-type dopings, a SiO$\sb2$ encapsulant enhances interdiffusion as compared to Si$\sb3$N$\sb4$. Silicon IILD is also investigated in the open-tube, As-poor annealing regime. To achieve appreciable Si diffusion under these conditions requires the removal of the GaAs cap and the use of Al-reduced SiO$\sb2$ or Si$\sb3$N$\sb4$ as a Si diffusion source.