Photoluminescence characterization of ZnSe doped with Ga by bulk and planar doping techniques in molecular-beam epitaxy

Abstract

Room-temperature and low-temperature (1.7-K) photoluminescence (PL) characteristics of heteroepitaxial ZnSe layers on GaAs which are doped with Ga by either conventional (bulk) or planar doping techniques are described. Low-temperature PL peaks at 2.27 and 2.0 eV involving deep acceptor levels are introduced by Ga doping, as well as newly reported shallow acceptor levels with binding energies of approximately 68 and 85 meV. The behavior of these peaks and the excitonic transitions is studied as a function of Ga-doping level and, for the case of the planar-doped layers, surface stoichiometry during doping. The exciton peaks exhibit substantially greater broadening for doping on Zn-rich surfaces than for Se-rich surfaces, corresponding to the higher carrier concentrations observed by electrical measurements in the former case. The deep acceptor levels are found to be incorporated to a lesser degree for doping on Zn-rich surfaces, while the incorporation of the 85-meV acceptor is enhanced in this case. The net electrical compensation is evidently dominated by the behavior of the deep levels. The results are explained by assuming that both deep levels involve donor-Zn vacancy complexes, whose formation is suppressed by the excess Zn flux supplied during the planar-doping process. A comparison of the exciton spectra of nominally undoped and bulk Ga-doped samples is used to demonstrate that the residual donor in the undoped material is Ga.

Effect of ZnSe/GaAs interface treatment in ZnSe quality control for optoelectronic device applications

“…Emission in this energy range may also be affected by the presence of Ga impurities. Reference 24 reported that Ga-doped ZnSe exhibited a peak around 2.0 eV when the Ga concentration was high, while a peak around 2.2 eV was more prominent when the Ga concentration was low [21].…”

“…5b and d). This transformation can be attributed to a competition between emission from shallow states near the band edge and emission from the impurities and native and extended defects that contributes to the DLE and Y 0 bands [21]. Thus, preparation of the ZnSe/GaAs interface with an As-rich surface and a Zn-PT is favorable to realizing ZnSe epilayers with lower impurity and defect densities and higher optical quality.…”

Competition of Deep and Shallow Impurities in Wide‐Gap II‐VI Semiconductors under Pressure

“…Comparison of ZnSe PL spectra at 1 atm (7 K) for (a) the same high purity undoped film, (b), (c), and (d) samples doped with the acceptors N, P, and As, respectively nated by bound excitons due to the intentional dopant (i.e., Ga, C1, N, P, or As). The DAP lines (2.55 to 2.75 eV) arise from shallow states of the majority dopant and of various residual impurities having the opposite polarity [42]. Broad 'midgap' PL bands are common in ZnSe and other 11-VI materials.…”

Investigation of radiative and nonradiative trap centers in ZnSe:Al layers grown by molecular beam epitaxy

“…[9][10][11] The level emission at 2.05 and 2.27 eV has also been reported in ZnSe:Ga layers where Ga is positioned on the same column as Al in the periodic table and has a similar atomic radius to Al. 17,18 In the case of ZnSe:Ga layers, it has been found that the concentration of V Zn increases with the increase of incorporated Ga concentration and strong emission near 2.05 eV found in ZnSe:Ga is ascribed to a Ga Zn V Zn complex defect. 18,19 Consequently, it is expected that the radiative trap centers RD1 and RD2 found in a heavily doped ZnSe:Al layer are ascribed to an Al donor complex defect and a V Zn -related defect.…”