Deep trap characterization in Si-doped In_0.52Al_0.48As/InP under hydrostatic pressure: a search for DX centres

Abstract

Deep levels have been characterized in Si-doped and undoped InAlAs layers lattice matched to InP. At ambient pressure and low temperature. the Schottky junction capacitance shows a small persistent photocapacitance effect, related to photoionization thresholds at 0.6 and 1.1 eV. Deep-level translent spectroscopy spectra show a dominant, low-density electron trap at around 320 K, with an emission energy very dependent on the bias conditions and t h e hydrostatic pressure (0.5 to 0.9 eV). This is attributed to an interaction of a high density of interface states with the trap emission process. Under hydrostatic pressure, neither the PPC per cent nor the OLTS spectra shape changes. Photoluminescence spectra in both Sidoped and undoped InAlAs layers show two weak peaks at 0.80 and 0.95 eV, that we suggest are due to a native defect involving an As antisite. W e conclude that the detected traps have no relation with the DX centres.

Shubnikov–de Haas effect and persistent photoconductivity in In0.52Al0.48As

“…This is a result of the wide dopant distribution in B689 and the correspondingly closer energy separation between states near the top of the potential well. The total increase in the free electron density for sample B689 is thus Ͼ2ϫ10 11 cm Ϫ2 while that for A1337 (N D ϳ5ϫ10 12 cm Ϫ2 ) is 1.6 ϫ10 11 cm Ϫ2 , comparable to the increase after illumination in the two dimensional electron density of an InGaAsInAlAs modulation doped heterostructure reported by Lo et al 7 PPC in InAlAs has been ascribed to both intrinsic [8][9][10] and extrinsic defects; 11,12 for example, native defects involving an As antisite 9 and deep acceptor states 10 have both been proposed. Recently, Sari and Wieder 11 have observed PPC in In 1Ϫx Al x As (0.1рxр0.34) due to DX centers which pin the Fermi level (E F ) to an average energy 0.3 eV below the lowest conduction band minimum.…”

Evidence for the occupation of DX centers in In0.29Al0.71As

“…If the scattering sites are correlated in a DX Ϫ Ϫd ϩ configuration, then the mobility measured at the 2DEG interface will be higher than for uncorrelated defects. If there are correlated DX centers in the In 0.29 Al 0.71 As, the mobility will increase the higher the cooling bias, as shown in the figure. center in AlAs, the alloy region where Calleja et al 6 claim not to find DX centers, and the depth of the level measured in this work. While Hong et al 5 measured an emission energy of 0.37 eV and a photocapacitance turn on at 0.61 eV, it is unclear where to place their data, since they did not publish a thermal ionization energy.…”

“…6 suggests that no DX centers would be occupied in lattice-matched InAlAs/InP, because the energy level would be resonant with the conduction band. That no DX centers were found under pressure by Calleja et al 6 could be due to the need to dope the material more heavily than 1ϫ10 18 cm Ϫ3 .…”

“…Although Nakashima et al 4 believed they had found DX centerlike behavior, other researchers, 5-7 using a combination of techniques, concluded that the traps found are not DX centers. Furthermore, Calleja et al, 6 subjected the material to 12 kbar of hydrostatic pressure roughly equivalent to the band structure of In 0.40 Al 0.60 As. They found no evidence of DX centerlike behavior.…”

Optical properties of compositionally graded InxAl1–xAs/GaAs heterostructures

“…The composition dependence of the energy levels of the DX centers in In x Al 1-x As/GaAs heterostructures has been determined by means of Hall effect and persistent photoconductivity measurements [10].…”