Density of states evaluations from oscillating/moving grating techniques

In this paper we first present a comparison between two grating techniques, the oscillating photocarrier grating (OPG) and the moving grating technique (MGT). The common origin of both techniques suggests that they should give the same experimental data. In this work we present measurements performed with both techniques and show their equivalence. Regarding the fact that the OPG method uses a lock-in amplifier to measure the photocurrent, while the MGT uses an electrometer due to its dc nature, we show that these techniques can be used in a complementary way, using the benefits that each one of them offers. Moreover, we present measurements of the density of states (DOS) of an amorphous silicon sample, which were made using a range of temperatures that are only achievable using both techniques. We also present a brief summary of the theory supporting these techniques, and we outline future research to improve the DOS estimation.

► We compare the OPG and the MGT grating techniques.
► We experimentally demonstrate the equivalence between both techniques.
► We present measurements of the density of states (DOS) of an a-Si sample.
► The DOS in the upper half of the bandgap can be accurately determined.
► This is only possible by combining both techniques.