Tunneling escape rate of electrons from quantum well in double-barrier heterostructures

A tunneling escape rate 1/${\mathrm{\tau }}_{\mathrm{T}}$ of electrons from a single quantum well through thin barriers was successfully determined by measurement and analysis of the lifetime ${\mathrm{\tau }}_{\mathrm{e}}$ of electrons generated in 6.2-nm GaAs single quantum wells by a picosecond laser pulse. The measured ${\mathrm{\tau }}_{\mathrm{e}}$ was found to decrease systematically as the AlAs barrier thickness ${\mathrm{L}}_{\mathrm{B}}$ was reduced. The ${\mathrm{\tau }}_{\mathrm{e}}$ for ${\mathrm{L}}_{\mathrm{B}}$<4 nm was found to agree very well with the lifetime ${\mathrm{\tau }}_{\mathrm{T}}$ predicted from the energy width of the resonance transmission. Irrelevance of coherence versus incoherence in the tunneling escape process is also pointed out.