Russian Physics Journal, Vol. 44, No. 1, 2001 1064-8887/01/4401-0061$25.00 2001 Plenum Publishing Corporation 61 MECHANISM FOR CONVERSION OF THE CONDUCTIVITY TYPE IN ARSENIC-DOPED p-Cd x Hg 1–x Te SUBJECT TO IONIC ETCHING V. V. Bogoboyashchii, A. P. Vlasov, and I. I. Izhnin UDC 621.315.592 Based on an analysis of chemical diffusion of mercury in p-Cd x Hg 1–x Te:As narrow-band solid solutions, a mechanism for conversion of the conductivity type upon ionic etching is suggested. It is shown that the n–p conversion of the conductivity in this case is due to the formation of a donor complex between arsenic in the Te sublattice and an interstitial Hg atom. Moreover, the electron concentration in the converted layer corresponds to the concentration of the implanted arsenic impurity. The theoretical results are confirmed by the experimental investigation of the electron concentration distribution over the n-layer of a p-Cd x Hg 1–x Te:As epistructure converted upon ionic etching. INTRODUCTION At present the n-p conversion of the conductivity type in vacancy-doped p-Cd x Hg 1–x Te (CHT) subject to ionic or plasma etching (IE or PE) has already been proved [1–9]. The general behavior of the properties of vacancy-doped p- Cd x Hg 1–x Te subject to etching has also been well studied experimentally. As was demonstrated, after IE [1–6] or PE [7, 9] the n-p conversion of the conductivity type was observed to a certain depth determined by the ion fluence, the acceptor (Hg vacancy) concentration in the parent material, the composition of the solid solution, and the temperature of the sample subjected to treatment. The conversion of the conductivity type in vacancy-doped p-Cd x Hg 1–x Te subject to etching is connected with the recombination of residual intrinsic acceptor defects – mercury vacancies (V Hg ) – with interstitial mercury atoms (Hg I ) generated in abundance in the subsurface region of the crystal subject to ion bombardment and diffused into its depth. The most typical feature of such conversion is a superhigh mercury diffusion rate (the mercury diffusion front acceleration is about 10 5 times that higher than that recorded for annealing in Hg vapors). Superhigh Hg diffusion rates upon bombardment of vacancy-doped p-Cd x Hg 1–x Te by low-energy particles in the process of IE were thoroughly examined in [10, 11]. Possible mechanisms of this phenomenon, which allowed qualitative and quantitative agreement with the experimental data to be obtained, were suggested there. The n-p conversion in As-doped p-Cd 0.3 Hg 0.7 Te [12, 13] and Au-doped p-Cd 0.3 Hg 0.7 Te epilayers [14] subject to jet ionic etching (JIE) has been reported recently. Smith et al. [12] and Siliquini et al. [13] used the laser beam induced current (LBIC) technique to establish conversion. In so doing, they did not study in detail the physical characteristics of converted layers; the concentration of carriers in the n-converted layer was determined by comparison of the theoretical and experimental LBIC signal waveforms. Antoszewski et al. [14], based on an analysis of the physical characteristics of the converted n-layer, concluded that the conversion of the conductivity type in this case was caused by the diffusion processes. Nevertheless, no mechanisms for conversion of the conductivity type were suggested in the above-indicated works. This calls for new experimental and analytical investigations into mechanisms of point defect interaction in this material. In the present paper, the influence of ionic etching on the electrophysical characteristics of As-doped p-Cd x Hg 1–x Te epilayers is examined, and a possible mechanism for the n-p conversion of the conductivity type upon such treatment is suggested. Kremenchug State Polytechnical Institute; I. Franko L’vov National University; L’vov Scientific-Research Institute of Materials at the Karat Research and Production Concern. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 50–58, January, 2001. Original article submitted December 5, 2000.