A Theory of Exciton Photoluminescence for Two Types of Neutral Acceptors in Silicon - A Study of the Systems Si: (B,In), Si: (Al,In), Si: (Ga,In), Si: (B,Al), Si: (B,Ga), and Si: (Al,Ga).
Interim rept. Jun 83-Aug 84,
DAYTON UNIV OH RESEARCH INST
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Rate equations for the densities of free excitons and excitons bound to two types of neutral acceptors in silicon are solved for steady state in the absence of saturation. These rate equations contain the terms for the tunneling of an exciton bound to one type of neutral impurity to another. The tunneling rates are calculated using a simple model of an exciton in a one-dimensional semi-infinite double potential well. The energy eigenvalue equation for an exciton in this potential well is derived for estimating the exciton tunneling time. The steady-state solutions of the rate equations yield an expression for the ratio of the bound exciton luminescence intensity as a function of the impurity concentrations. The relative photoluminescence intensities for the systems SiB,In, SiAl,In, SiGa,In, SiB,Al SiB,Ga, and SiAl,Ga are calculated for various values for the relative free exciton capture cross section ratios. This model predicts no exciton tunneling for any of the above systems for the low impurity concentration range. For the systems with large differences in the bound exciton energy levels such as SiB,In, SiAl,In, and SiGa,In, it predicts quenching of shallow impurity bound exciton luminescence. For the systems with small differences in the bound exciton energy levels such as SiB,Al and SiB,Ga, the theory predicts enhancement of shallow impurity bound exciton luminescence. For the system SiAl,Ga in which the difference in the bound exciton energy levels is very small, gallium bound exciton luminescence dominates if the aluminum free exciton capture section is less than the gallium free exciton capture cross section.
- Solid State Physics