Transport Modeling and Compensation Mechanism for Semi-Insulating LT-Gaas and InP: Cu
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TRANSPORT MODELING AND COMPENSATION MECHANISM FOR SEMI-INSULATING LT-GaAs AND InP: Cu
K. Xie, and C.R. Wie Department of Electrical and Computer Engineering, State University of New York at Buffalo Buffalo, New York 14260
ABSTRACT The compensation mechanism and transport properties of annealed GaAs grown by molecular beam epitaxy at low substrate temperature (LT-GaAs) and Cu diffused InP are analyzed by using a deep donor band model and a precipitate model. It was found that the compensation in highly resistive LT GaAs can not be explained by the precipitate model alone, and therefore a high donor density had to be considered. In Cu diffused InP, the precipitate model gives a consistent explanation for the observed carrier compensation and mobility data. For both semi-insulating LT-GaAs and fully-compensated, lightly-doped InP:Cu, the neutral impurity scattering was found to be a major carrier scattering mechanism.
INTRODUCTION Since Smith and Calawa [1] first reported the molecular beam epitaxy (MBE) growth of GaAs layer at low substrate temperature (LT-GaAs) and its successful application as a buffer layer in FET devices, there has been a great progress made in both application and understanding of material properties of LT-GaAs (2-6]. LT-GaAs is highly resistive after annealing at 600 0C. It is known that, in LT-GaAs, there exists over 1 at% excess As. AsGa antisite defects are 19 3 on the order of 10 /cm in as grown LT-GaAs[3], and As precipitates are on the order of 1017/ 3 0 cm in 600 C annealed LT-GaAs[5]. The unusual high density defects play a key role in determining the LT-GaAs material properties. In regarding to the compensation mechanism, there are two models: deep donor band model proposed by Look et al.[6] and As precipitate model by Warren et al.[7]. In Look's model, a EL2 deep donor band is assumed as the major compensation centers, similar to the case of undoped semi-insulating bulk GaAs, except the density of EL2 level is much higher in LT-GaAs. It was reported that the high density of EL2 level in LTGaAs annealed above 500 0 C was measured by the photoabsorption measurement[8]. However, this model failed to explain the semi-insulating behavior of annealed Si doped LT-GaAs. Based on the transmission electron microscopy (TEM) observation, Warren et al. suggested that overlapping of the depletion regions surrounding the As precipitates could explain the semi-insulating behavior of both undoped and doped LT-GaAs. Recently, Leon et al. [9] reported that Cu diffusion in InP could lead to the formation of semi- insulating lnP. It was suggested that Cu precipitate may be responsible for the semi-insulating properties of InP:Cu based on the TEM observation. Thus, it is of great interest to analyze the compensation and transport properties of both LT GaAs and InP: Cu based on the two models.
COMPENSATION AND TRANSPORT PROPERTIES OF LT-GaAs 0 The 5 ILtm thick undoped LT-GaAs layer grown at 200 C was used in this study. There is
Mat. Res. Soc. Symp. Proc. Vol. 241. @1992 Materials Research Society
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