DOI: 10.1007/s00339-003-2285-3 Appl. Phys. A 80, 167–171 (2005) Materials Science & Processing Applied Physics A e. ozturk 1, ✉ h. sari 1 y. ergun 1 i. sokmen 2 The triple Si δ-doped GaAs structure 1 Cumhuriyet University, Department of Physics, 58140 Sivas, Turkey 2 Dokuzeylul University, Department of Physics, 35230 Izmir, Turkey Received: 16 January 2003/Accepted: 1 July 2003 Published online: 16 September 2003 • © Springer-Verlag 2003 ABSTRACT For the uniform donor distribution we have the- oretically investigated the influence of the separation between the adjacent two doping layers on the electronic structure of the triple Si δ-doped GaAs, at T = 0 K. To find the subband structure of the triple δ-doped quantum well we have solved self-consistently both Schr¨ odinger and Poisson equations. From our calculations, we have seen that the electronic properties of triple Si δ-doped GaAs structure depend strongly on the spacer thickness between the adjacent two doping layers. In this study, we can estimate that the mobility in closely spaced triple δ-doped GaAs structures is very high compared to single δ-doped structures because of the overlap between the elec- tron wave function and the ionized scattering centres in single δ-doped structures. PACS 73.90.+f 1 Introduction Recently, rapid advanced material-growth technol- ogy such as molecular beam epitaxy (MBE) technique enable the growth of abrupt high-concentration doping profiles. The confinement of the donors has been shown to be very narrow and the concept of planar or delta-δ-doping has been intro- duced. Delta doping is an important technique widely used in a number of semiconductor devices. In a semiconductor a one-dimensional doping profile can be considered to be δ- function like, if the thickness of the doped layer is smaller than other relevant length-scales. Such narrow doping profiles can be mathematically described by the Dirac’s δ function [1], i.e. N d (z ) = N 2D d δ(z ), where N 2D d is the 2 D donor concentra- tion. It was found that in the high-density limit the distribution of donors is random, whereas in δ-doped semiconductor the donors are confined in a few atomic layers of crystal, thus this profile (δ-doped case) neglects the random distribution of donors in the doped layer [2]. There has been a rapidly growing interest in the use of delta (δ, planar)-doping in semi- conductor structures for a range of technological applications in electronic and photonic devices and as a source of basic research [3–14]. ✉ Fax: +90-34/6212-1186, E-mail: eozturk@cumhuriyet.edu.tr Silicon is widely used as the n-type dopant in GaAs growth using molecular beam epitaxy (MBE). When Si donors are localized into an atomic plane during epitaxial growth, a sheet of ionized donors produces a V -shaped po- tential well which confines the electron along the direction perpendicular to a δ-doped plane and leads to formation of a quasi-two-dimensional electron gas (2DEG). The eigen- states of such 2DEG depend on the shape of the space-charge potential. The electronic structure of the system has been cal- culated by solving the Schrödinger and Poisson equations self-consistently. In order to fabricate high-mobility δ-doped devices, some works are focused in improving doping and material growth techniques [15, 16]. An alternative way to improve the elec- tron mobility in the δ-doped semiconductors, which has been proposed recently, is to make a structure with double δ-layers [17–23]. The enhancement in mobilities and concen- trations in these structures are due in part to the fact that more carriers distribute at the centre of the two δ-doped GaAs wells. In these structures the carrier transport is spatially separated from ionized impurity scattering centres and consequently the electron mobility is increased by two to five times over that of a single δ-doped case [17]. Thus, triple δ-layer structures open up the possibilities for higher electron mobility than those in single layer systems. In this study, we have investigated theoretically the elec- tronic properties of the triple Si δ-doped GaAs by solving the Schrödinger and Poisson equations self-consistently, at T = 0K. We try to analyse the mobility behaviour in triple δ-doped structures by overlap of the wave function with the scattering centres. By using this method we can esti- mate the effect of the separation between the δ-layers on the mobility qualitatively. However, the electron mobility in Si δ-doped structures is known to be strongly affected by self- compensation of Si atoms as well as by spatial correlations of charged impurities [24–26]. S.M. Shi have shown the im- portance of correlation effects of charged impurities clearly, especially for the lowest subband and they have concluded that in order to investigate the influence of DX centers on the transport properties of δ-doped GaAs effectively one has to use samples with relatively low doping density, so that mechanisms such as clustering and self-compensation can be neglected. In order to investigate the spatial correlations of charged impurities on the electron mobility we have studied