Imaging transport for the determination of minority carrier diffusion length

A scanning electron microscope technique is used, in combination with an optical imaging system, to measure minority carrier diffusion length in a heavily doped GaAs double heterostructure. Diffusion and drift of charge are imaged. A diffusion length of 3.6μm is measured, corresponding to a minority carrier mobility of 1150cm2∕Vs in p-type material doped ∼5×1018cm−3. Measurements are made as a function of local electric field and sample temperature. The technique offers a flexible approach to direct measurement of transport properties and is applicable to a range of luminescent materials and multilayer devices.