Effect of temperature on the electron distribution in illuminated heterostructures

We solve the 1D Poisson equation for a model heterostructure containing photoexcitable donors and derive solutions for different temperatures in the range 77–300 K. We consider a single-interface GaAs/${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As heterostructure having deep donors in both the ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As supply layer and in the GaAs buffer, but our approach is applicable to other configurations. The calculation accounts for photogenerated electrons arising from simulated DX centers in the ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As layer and from impurity donors in the GaAs buffer. Using realistic parameters in a quantitative calculation applicable to steady illumination, we show how light affects the internal distribution of free electrons among the active layers. The results give a transparent picture of the factors that control the response of a unipolar heterostructure to light at different temperatures.