Photoelastic Waveguides Formed by Interfacial Reactions on Semiconductor Heterostructures

Abstract

Lateral confinement of carriers and photons in semiconductor heterostructures is an important feature in modern electronic and optoelectronic devices. A number of techniques have been invented to induce lateral confinement with varying degrees of success and processing requirements. One of simplest but least commonly used technique is to utilize the strain induced effect (or the photoelastic effect) to cause confinement. While the concept is simple, the control of stress in the stressor layers is rather difficult in practice, without resorting to complicated selective growth of strained layers. We have investigated the controlled introduction of stable stresses into semiconductor heterostructures using a simple scheme of interfacial reactions between a metal and the substrate. Since the volumetric change for a given reaction is fixed, the induced stress in the structure is independent of the deposition method or the deposition system, as long as the deposited film is fully reacted to form a compound. The stability of the stress depends on the stability of the compound. We have made low-loss (~ 1dB/cm at 1.53 μm) photoelastic waveguides in GaAs/AlGaAs and other layered structures by reacting Ni and other metals, with an underlying semiconductor. In the case Ni on GaAs/AlGaAs, the dominant stressor compound is Ni₃GaAs, and the waveguide characteristics are thermally stable up to 600°C. Other photoelastic optical devices are also demonstrated.