Spectroscopic method of strain analysis in semiconductor quantum-well devices

Abstract

The modification of the electronic bandstructure in a semiconductor, quantum well due to an induced strain is well known. Recently, we have developed a generalized, spectroscopic-based technique for analyzing the strain condition within devices based on quantum wells. This approach couples experimental data describing interband transition energies within strained, quantum-well devices with a rigorous theoretical description of the quantum-well bandstructure. The theoretical formalism is described, and various important theoretical predictions necessary in the application of this method are given. The accuracy of the theoretical model used in this approach is critical to its success, and it is therefore necessary to ensure the validity of the theoretical formalism as applied to quantum wells under a variety of strain conditions. We show the good agreement between theory and experiment for a number of known strain conditions within quantum wells and quantum-well devices. This agreement indicates the validity of the theoretical formalism in the method being described, and the applicability of the method to a wide class of quantum-well based semiconductor devices. A key result in applying this method is the piecewise linearity of the change in interband transition energy with strain for the ranges of strain of interest. The method is then applied to the important case of packaging-induced strain in high-power diode lasers or “cm-bars” as they are sometimes known. Experimental results indicate that the method provides an excellent means of analyzing packaging-induced strain in cm-bars and similar devices.