Theoretical and experimental investigations of subpicosecond photoconductivity

Monte Carlo methods are used to study photoconductive transients in gallium arsenide. It is demonstrated that working with presently established ranges for the Γ-L coupling coefficient, the existence of a velocity overshoot at moderate fields cannot be exactly predicted. The role of negative velocity electrons in the initial transient for short wavelength excitation is also demonstrated. Details of an actual experiment are described and evaluated against a model which incorporates the Monte Carlo simulation into a transmission line structure with a frequency-dependent characteristic impedance. The results demonstrate that an appropriately designed experiment can observe subpicosecond carrier transport transients.