Surface Structure of Molecular Beam Epitaxy (211)B HgCdTe

Abstract

The as-grown molecular beam epitaxy (MBE) (211)B HgCdTe surface has variable surface topography, which is primarily dependent on substrate temperature and substrate/epilayer mismatch. Nano-ripple formation and cross-hatch patterning are the predominant structural features observed. Nano-ripples preferentially form parallel to the ½ " 111 and are from 0 Å to 100 Å in height with a wavelength between 0.1 lm and 0.8 lm. Cross-hatch patterns result from slip dislocations in the three {111} planes intersecting the (211) growth surface. The cross-hatch step height is 4 ± 1 Å (limited data set). This indicates that only a bi-layer slip (Hg/Cd + Te) in the {111} slip plane occurs. For the deposition of MBE (211)B HgCdTe/CdTe/Si, the reorientation of multiple nano-ripples coalesced into ''packets'' forms cross-hatch patterns. The as-grown MBE (211)B CdTe/Si surface is highly variable but displays nanoripples and no cross-hatch pattern. Three types of defects were observed by atomic force microscopy (AFM): needle, void/hillock, and voids.

Surface Morphology and Defect Formation Mechanisms for HgCdTe (211)B Grown by Molecular Beam Epitaxy

“…Some crosshatch structures on MBE-grown HgCdTe (211) surfaces were of very small height, namely 0.4 nm, which is slightly larger than an atomic step on a (211) surface. These are designated ''crosshatches'', and are actually caused by surface strain relief 9,26 and dominated by slight lattice deformation without formation of misfit dislocations. Surface strain relief and misfit dislocation formation are two competing mechanisms that can coexist within the same sample.…”

“…Large void defects with sizes from several micrometers to tens of micrometers are the most common defect in MBE-grown HgCdTe. They arise as a consequence of Hg-deficient growth conditions, and are called either voids, 1,9,[40][41][42][43][44][45][46][47][48][49][50] crater defects, 6,10,22,23 V-shape 37 The directions of the crosshatched lines as well as the characteristic angles are labeled. The arrows show that the crosshatch lines are sometimes terminated by etch pits, namely dislocations in the crystal.…”

“…9,40,55,60 They are stoichiometric and always show one ridge that is higher than the other. Such differences are usually smaller at the tip of a needle defect, as shown in Fig.…”

“…It has been demonstrated to be a valuable nondestructive multipurpose microscopic research tool for studying HgCdTe-related materials. [9][10][11][12][13][14][15][16][17][18][19][20][21] In this work, a Veeco D3100 scanning probe microscopy (SPM) system configured for tapping-mode operation was used for AFM measurements. A 1-X Si tapping-mode tip/ cantilever with a backside Al reflective enhancement coating was employed to obtain good signal-tonoise ratio.…”

Molecular Dynamics Simulation of MBE Growth of CdTe/ZnTe/Si

“…The US Army considers the development of Si-based substrates for HgCdTe a top priority. 3 Over the past decade, several research groups, including EPIR Technologies, Inc., [4][5][6][7][8][9][10][11][12][13] the Microphysics Laboratory 14 at the University of Illinois at Chicago, the Army Research Laboratory, 15 the Night Vision Laboratory, 16 Raytheon Vision Systems, 17 Hughes Research Laboratory, 18 and Teledyne 19 have carried out intensive research on growth of CdTe on Si by molecular beam epitaxy (MBE) for that purpose. As a result of this community-wide effort, CdTe/Si has reached a level of maturity to compete with bulk CdZnTe as a substrate for mid-wave infrared (MWIR) HgCdTe applications.…”