i PHILOSOPHICAL MAGAZINE B, 1985, VOL. 52, No.3, 759- 784 Indentation plasticity and polarity of hardness on {Ill} faces of GaAs By P. B. HIRSCH , P. PIROUZ t, S. G. ROBERTS and P. D. WARREN Dcpartment of Metallurgy and Science of Materials, Univcrsity of Oxford, Parks Road , Oxford OX 1 3PH, England [Receit:ed 4 March 1985 alld w;cepled 1 April }\iS5] ABSTRACT Hardness measurements have been carried out as a function of temperature on : Ill } faces of n- and p-type GaAs. The plastic zone ha s been studied by observations of slip-linc patterns on the surface and dislocation etch pit patterns in sections at different dcpths from the indentation wrface. The nature of the plastic zone, the types of cracks ohserved, the recovery slip after removal of the load and the polarity in hardness have been explained in detail in terms of slip geometry. sense and type of slip expected, dislocation interactions and the known differences in velocities of As(g) and Ga(g) di slocations. 1. INTRODUCTIO t\ Nevill Mott's contributions to the theory of electronic and mechanical properties of the solids are legion. In this paper we describe an effect of polarity in hardness of III-V compound semiconductors and explain it in terms of an anisotropy in dislocation velocity, which has its origin in deep levels associated with dislocations in these materials. This work thus connects a mechanical property , in this case hardness, a subject in which Mott made a contr ibution 40 years ago (Bishop. Hill and Mott 1945), with electronic properties of semiconductors , central to his interests over many years. The hardness of (Ill) and (TIT ) faces of crystals of III-V compounds is generally different: in most cases reported in the literature the surface terminating in group-III element atoms is harder than that terminating in group-V element atoms (Shimizu and Sumino 1970, Gatos and Lavine 1965, Maeda, Ueda, Murayama and Sakamoto 1977). In GaAs ourcxpcr,iments, using a Vickers indenter , show this to be so for n-type material over the whole temperat ure range studied (fig. 1 (a)), t he difference between t he hardness of the two faces heing about 25'\ , at 400 C, but for p-type material the As face is harder than the Ga face (fi g. l(h)). It is aliso known that dislocations in IJI-V comp o unds have diiTerent velocities depend i ng on whether ( he extra half-planes termina te on rows of Groll p-II I or Grou p- V atom s (Choi, Mihara and Ninomiya 1977, 19711, Erofeeva and Ossipyan 1973, Mihara and Ninomiya 1975, Ninomiya 1979, Maeda et al. 1977). The polarity of hardness is likely to be related to the anj sotropy of dislocation velocity through the slip systems operating in the stress fidd under the indenter. The crystallography of slip is therefore very important, and models of the plastic zone based on spherically symmetrical expanding cavities (Marsh 1964) or a blister field (Yoffe 1982) are not appropriate to this case , when t he plastic zo ne is expected to be anisotr opic. ,. Now at Department of Metallurgy and Materials Science. Ca se Western Reserve University. Cleveland, Ohio 44106, U.S.A.