Band-edge modifications due to photogenerated carriers in singlep-type δ-doped GaAs layers

Abstract

The photogenerated carrier-induced band-edge modifications of beryllium single ␦-doped GaAs layers comprising a two-dimensional hole gas ͑2DHG͒ were investigated by means of photoluminescence, selective photoluminescence, and photoluminescence excitation spectroscopies. The results show direct evidence for a photoinduced electron confinement effect, which strongly enhances the radiative-recombination probability between electrons and holes of the 2DHG at low temperatures. ͓S0163-1829͑99͒01607-0͔Delta-doped structures have already been extensively investigated as they represent the state of the art in doping profile and became quite important for the microelectronic industry. 1 Although the n-type ␦-doping structures have received a great deal of attention so far, only recent the p-type ␦-doping structures became the subject of systematic investigations. 2-4 One remarkable contrast between these two systems is the fact that in photoluminescence ͑PL͒ measurements carried out on single isolated ␦-doped layers, the expected two-dimensional ͑2D͒ emission bands are only observed in p-type, but not in n-type structures. Moreover, the observed temperature dependence of the PL emission bands associated with the two-dimensional hole gas ͑2DHG͒ in p-type ␦-doped layers exhibits an interesting thermal quenching effect that has attracted interest recently. [4][5][6] It has been argued that the thermal quenching (T ϳ60 K) of the 2DHG-related emission band from p-type ␦-doped GaAs layers was probably due to the escape of holes from the ␦-potential well to the nearby bulk material. 6 However, the rapid thermal quenching (Tϳ12 K) observed in p-type Si layers by Buyanova and co-workers was explained in terms of a shallow electron-potential well induced by photoexcited holes, which are captured by the ␦-doping well. 4 According to this model, the quenching of the 2DHG luminescence is due to the thermal activation of confined electrons from the photoinduced-potential well to the continuous states in the host material.The comparison between the luminescence spectra from n-and p-type ␦-doping GaAs structures was recently performed through rigorous self-consistent band-structure calculations. 5 It was particularly emphasized the role played by the photoinduced electron-confinement effect on the realistic description of the PL spectra from p-type ␦-doped structures. In the present paper we report on the results obtained by means of PL, selective photoluminescence ͑SPL͒, and photoluminescence excitation ͑PLE͒ spectroscopies of Be ␦-doped GaAs structures. The aim of the paper is to provide direct evidence for such photoinduced effect as proposed by Buyanova and co-workers and confirmed by theory. A set of three samples was grown by molecular beam epitaxy on a semi-insulating GaAs ͑001͒ substrate. The samples comprise a 0.42-m-thick GaAs buffer layer, a plane of Be atoms, a 0.18-m-thick undoped GaAs layer, and a 50-A-thick Be-doped GaAs cap layer ( pϭ2 ϫ10 18 cm Ϫ3 ). The growth temperature was 580°C for the buffer layer and 520°C for t...

Effects of thermally activated hole escape mechanism on the optical and electrical properties inp-type Si δ-dopedGaAs(311)Alayers

“…1,2 From a fundamental point of view, ␦-doped layers provide interesting systems for studying the fundamental properties of a two-dimensional carrier gas in the limit of strong coupling with the ionized impurities of the ␦-doped layers. Although several theoretical and experimental works have already been devoted to the study of the fundamental properties of single, [3][4][5] double, 6,7 and multiple ␦-doped (M␦D) layers, [8][9][10][11][12][13][14][15][16][17][18][19][20] in GaAs most of them were related to n-type ␦-doped layers. Little is known about the relevant mechanisms that limit the mobility of the two-dimensional hole gas ͑2DHG͒, as well as which ones control its temperature dependence in p-type M␦D GaAs layers.…”