Characterization of Hg0.7Cd0.3Te n- on p-type structures obtained by reactive ion etching induced p- to n conversion

This paper presents transport measurements on both vacancy doped and gold doped Hg0.7Cd0.3Te p-type epilayers grown by liquid phase epitaxy (LPE), with N-A = 2 x 10(16) cm(-3), in which a thin 2 mu m surface layer has been converted to n-type by a short reactive ion etching (RIE) process. Hall and resistivity measurements were performed on the n-on-p structures in van der Pauw configuration for the temperature range from 30 K to 400 K and magnetic field range up to 12 T. The experimental Hall coefficient and resistivity data has been analyzed using the quantitative mobility spectrum analysis procedure to extract the transport properties of each individual carrier contributing to the total conduction process. In both samples three distinct carrier species have been identified. For 77 K, the individual carrier species exhibited the following properties for the vacancy and Au-doped samples, respectively, holes associated with the unconverted p-type epilayer with p approximate to 2 x 10(16) cm(-3), mu approximate to 350 cm(2)V(-1)s(-1), and p approximate to 6 x 10(15) cm(-3), mu approximate to 400 cm(2)V(-1)s(-1); bulk electrons associated with the RIE converted region with n approximate to 3 x 10(15) cm(-3), mu = 4 x 10(4) cm(2)V(-1)s(-1), and n approximate to 1.5 x 10(15) cm(-3), mu approximate to 6 x 10(4) cm(2)V(-1)s(-1); and surface electrons (2D concentration) n approximate to 9 x 10(12) cm(-2) and n approximate to 1 x 10(13) cm-2, With mobility in the range 1.5 x 10(3) cm(2)V(-1)s(-1) to 1.5 x 10(4) cm(2)V(-1)s(-1) in both samples. The high mobility of bulk electrons in the RIE converted n-layer indicates that a diffusion process rather than damage induced conversion is responsible for the p-to-n conversion deep in the bulk. On the other hand, these results indicate that the surface electron mobility is affected by RIE induced damage in a very thin layer at the HgCdTe surface.