Mn Acceptor Level Research Articles

Characterization of the Mn acceptor level in GaAs

We report on deep-level transient spectroscopy investigations of the Mn acceptor level in GaAs, including measurements of the emission and capture of holes and of the capture of electrons. A comparison is made between electron capture rates obtained from space-charge techniques and from photoluminescence decay measurements.

The effect of hydrostatic pressure on the 0.15 eV Cu acceptor level in GaAs

The evolution of the characteristic photoluminescence (PL) of the 0.15 eV Cu acceptor level in GaAs has been studied as a function of hydrostatic pressure. In the pressure range up to 35 kbar, i.e. in the direct gap region, the Cu-related PL band closely tracks the near-band-edge emission. The pressure derivative of the Cu acceptor level has been determined and is found to be 0.3 ± 0.2 meV/kbar. This number is only a small fraction of the total pressure derivative of the Γ 1C− Γ 15V energy gap which amounts to 10.7 meV/kbar, a result similar to our previous findings for the Mn acceptor level in GaAs, for which the pressure derivative was found to be 1.2 ± 0.2 meV/kbar. It should be noted that the remaining difference in pressure derivative is significant and beyond the uncertainty of the experimental data.

Hydrostatic pressure effects on Mn in GaAs 1−xP x

Hydrostatic pressure has been applied to samples of Mn-doped GaAs and GaAs 1−xP x ( x=0.04). The charge transfer nature of the radiative recombination allows determination of the pressure derivative of the Mn acceptor level relative to the valence band edge. The pressure derivatives have been determined and are found to be identical for both the binary and ternary material, 1.1–1.2meV/kbar. This number is only a small fraction of the total pressure derivative of the Γ 1c−Γ 15v energy gap which amounts to 10.7meV/kbar. Using the Mn acceptor energy level as a reference we were able to determine the hydrostatic deformation potentials of the valence and conduction bands and found values of a v =+0.9 eV and a c =−7.7 eV respectively, in excellent agreement with recent theoretical values.

Manganese luminescence in AlGaAs-alloys and AlGaAs/GaAs quantum wells

Our low-temperature photoluminescence studies of Mn-doped Al xGa 1−xAs-alloys reveal a linear shift of the Mn-acceptor level with increasing Al-content x. Using the Mn-acceptor as a reference level, we determine a valence-band offset between GaAs and AlAs of ΔE v=0.33eV. At x≈0.25 the Mn-related donor-to-acceptor pair-transitions interchange with the internal d-shell transitions within the Mn-acceptor. Characteristic luminescence transitions in GaAs quantum wells doped with Mn are identified with the recombination of electrons with the Mn-acceptor bound holes. In these quantum wells, the Mn-level shifts with decreasing well-width parallel to the heavy-hole band.

Elimination of ionized impurity scattering in heavily doped GaxIn1−xAsyP1−y

Unexpectedly high hole mobilities occur in p-type layers of Ga0.03In0.97As0.07P0.93 grown by liquid phase epitaxy and concurrently doped with high concentrations (1017–1019 cm−3) of Mn and Ge. The temperature dependence of the hole mobility indicates that ionized impurity scattering is insignificant. The effect is attributed to the diffusion of neutral Mn to form donor-acceptor complexes instead of isolated ionized donors and acceptors. Such a model is consistent with observed diffusion profiles into a variety of substrates from Mn-doped epilayers and the presence of ionized impurity scattering where either the donor concentration or the depth of the Mn acceptor level is such that little or no neutral Mn is present.

Characterisation of Mn-doped and nominally pure LPE GaxIn1-xAsyP1-y (y=2.1x) between y=0 and y=1 using photoluminescence and electrical measurements

Photoluminescence (PL) and electrical measurements have been made on a series of p-type, Mn-doped layers of GaxIn1-xAsyP1-y (y=2.1x) grown by liquid phase epitaxy on InP substrates and of a similar series of nominally pure crystals used as control samples. For small y, the Mn-doped samples shown an intense Mn-related PL band with a zero-phonon structure at 1.185 eV (4K) for the y=0 (InP) sample. This locates the Mn-acceptor level at 230 meV above the valence band edge. The PL band can be followed up to y=0.40 and the Mn-acceptor energy EA is estimated to vary as (230-185y) meV. For larger y, a broad, though strong, PL is observed on the low energy side of the near-band-edge lines. At these higher y values, electrical measurements have been used to determine EA, giving EA=49 meV for y=0.93 and 0.10 eV for y=0.70, in fairly good agreement with linear extrapolation of the PL data. The low temperature PL of six undoped control samples (0.5<y<1) reveal two sharp PL lines at (1.02-0.33y) and (1.00-0.33y) eV of as yet unknown origin.

Photoluminescence of Mn doped epitaxial GaAs

We have measured the near band edge photoluminescence of Mn doped liquid phase epitaxially grown GaAs. The photoluminescence spectra at 2°K shows, at low excitation intensities, a structure of up to eight sharp peaks (widths .2 to 1.0 meV) between 1.517 and 1.512 eV, besides the lower energy bands near 1.41 eV due to the deep Mn acceptor level and the usual donor-acceptor bands around 1.47 eV. Attempts to relate the sharp lines to the Mn electronic states, introduced by doping, were unsuccessful. It is our belief that the presence of this particular impurity in our samples allows for whatever states are responsible for the sharp line structure, to reveal themselves in the emission spectrum. A most unespected result is that near band edge sharp line luminescence is observed for impurity concentration as high as 10 18cm -3.