Maximum entropy mobility spectrum analysis of HgCdTe heterostructures

We report on mobility spectrum analysis of p-type HgCdTe using a new maximum entropy algorithm termed full MEMSA (f-MEMSA). The algorithm is the first that separates the constraints on the transverse and longitudinal components of the conductivity tensor, which results in a higher resolution, compared to other MEMSA algorithms. Compared to the Lakeshore c-QMSA algorithm, f-MEMSA demonstrated a lower detection limit and smaller errors for estimations on synthetic data sets. f-MEMSA was applied to experimental data measured on p-type Hg_0.77Cd_0.23Te, measured between T=30 K and 300 K and for an applied magnetic field between μ₀H=0 T and 9 T. Despite the demonstrated high performance of f-MEMSA on synthetic data, we observed several nonphysical contributions, such as low mobility electrons and high mobility holes. A systematic study of different sample geometries and growth methods showed that the high mobility holes, so-called mirror peaks, can be attributed to finite contact size effects. It also indicated that the low mobility electrons appear in the mobility spectrum as a consequence of a limitation in the application of mobility spectrum analysis (MSA) to vacancy-doped HgCdTe, which is consistent with a magnetic freezeout of the holes at high magnetic fields.