TY - JOUR A1 - Becker, Charles R. A1 - He, L. A1 - Einfeldt, S. A1 - Wu, Y. S. A1 - Lérondel, G. A1 - Heinke, H. A1 - Oehling, S. A1 - Bicknell-Tassius, R. N. A1 - Landwehr, G. T1 - Molecular beam epitaxial growth and characterization of (100) HgSe on GaAs N2 - In this paper, we present results on the first MBE growth of HgSe. The influence of the GaAs substrate temperature as well as the Hg and Se fluxes on the growth and the electrical properties has been investigated. It has been found that the growth rate is very low at substrate temperatures above 120°C. At 120°C and at lower temperatures, the growth rate is appreciably higher. The sticking coefficient of Se seems to depend inversely on the Hg/Se flux ratio. Epitaxial growth could be maintained at 70°C with Hg/Se flux ratios between lOO and ISO, and at 160°C between 280 and 450. The electron mobilities of these HgSe epilayers at room temperature decrease from a maximum value of 8.2 x 10^3 cm2 /V' s with increasing electron concentration. The concentration was found to be between 6xlO^17 and 1.6x10^19 cm- 3 at room temperature. Rocking curves from X-ray diffraction measurements of the better epilayers have a full width at half maximum of 5S0 arc sec. KW - Physik Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-50947 ER - TY - JOUR A1 - Kraus, M. M. A1 - Becker, Charles R. A1 - Scholl, S. A1 - Wu, Y. S. A1 - Yuan, S. A1 - Landwehr, G. T1 - Infrared photoluminescence on molecular beam epitaxially grown Hg\(_{1-x}\)Cd\(_x\)Te layers N2 - No abstract available Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-38053 ER - TY - JOUR A1 - Wu, Y. S. A1 - Becker, Charles R. A1 - Waag, A. A1 - Schmiedl, R. A1 - Einfeldt, S. A1 - Landwehr, G. T1 - Oxygen on the (100) CdTe surface N2 - We have investigated oxygen on CdTe substrates by means of x-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED). A Te oxide layer that was at least 15 A thick was found on the surface of as-delivered CdTe substrates that were mechanically polished. This oxide is not easily evaporated at temperatures lower than 350°C. Furthermore, heating in air, which further oxidizes the CdTe layer, should be avoided. Etching with HCI acid (15% HCl) for at least 20 s and then rinsing with de-ionized water reduces the Te oxide layer on the surface down to 4% of a monoatomic layer. However, according to XPS measurements of the 0 Is peak, 20%-30% of a monoatomic layer of oxygen remains on the surface, which can be eliminated by heating at temperatures ranging between 300 and 340 cC. The RHEED patterns for a molecular beam epitaxially (MBE)-grown CdTe film on a (lOO) CdTe substrate with approximately one monoatomic layer of oxidized Te on the surface lose the characteristics of the normal RHEED pattems for a MBE-grown CdTe film on an oxygen-free CdTe substrate. Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37869 ER - TY - JOUR A1 - Becker, Charles R. A1 - Wu, Y. S. A1 - Waag, A. A1 - Kraus, M. M. A1 - Landwehr, G. T1 - The orientation independence of the CdTe-HgTe valence band offset as determined by x-ray photoelectron spectroscopy N2 - No abstract available Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30784 ER - TY - JOUR A1 - Wu, Y. S. A1 - Becker, Charles R. A1 - Waag, A. A1 - Bicknell-Tassius, R. N. A1 - Landwehr, G. T1 - Thermal effects on (100) CdZnTe substrates as studied by x-ray photoelectron spectroscopy and reflection high energy electron diffraction N2 - The influence of different CdZnTe substrate treatments prior to II-VI molecular beam epitaxial growth on surface stoichiometry, oxygen, and carbon contamination has been studied using x-ray photoelectron spectroscopy and reflection high energy electron diffraction. Heating the substrate at 300 °C can eliminate oxygen contamination, but cannot completely remove carbon from the surface. Heating at higher temperatures decreases the carbon contamination only slightly, while increasing the Zn-Cd ratio on the surface considerably. The magnitude of the latter effect is surprising and is crucial when one is using lattice matched CdZnTe (Zn 4%) substrates. Y1 - 1992 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37801 SN - 0003-6951 ER - TY - JOUR A1 - Wu, Y. S. A1 - Becker, Charles R. A1 - Waag, A. A1 - von Schierstedt, K. A1 - Bicknell-Tassius, R. N. A1 - Landwehr, G. T1 - Surface sublimation of zinc blende CdTe N2 - The surface sublimation of Cd and Te atoms from the zinc blende (111)A CdTe surface has been investigated in detail by reflection high energy electron diffraction and x-ray photoelectron spectroscopy. These experiments verify that Te is much easier to evaporate than Cd. The experimental value for the Te activation energy from a Te stabilized (111)A CdTe surface is 1.41 ±0.1O eV, which is apparently inconsistent with recent theoretical results. Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37829 ER - TY - JOUR A1 - Wu, Y. S. A1 - Becker, Charles R. A1 - Waag, A. A1 - Bicknell-Tassius, R. N. A1 - Landwehr, G. T1 - Removal of oxygen and reduction of carbon contamination on (100) Cd\(_{0.96}\)Zn\(_{0.04}\)Te N2 - No abstract available Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-38014 ER - TY - JOUR A1 - Becker, Charles R. A1 - He, L. A1 - Regnet, M. M. A1 - Kraus, M.M. A1 - Wu, Y. S. A1 - Landwehr, G. A1 - Zhang, X. F. A1 - Zhang, H. T1 - The growth and structure of short period (001) Hg\(_{1-x}\)Cd\(_x\)Te-HgTe superlattices N2 - Molecular beam epitaxially grown short period (001) Hg\(_{1_x}\)Cd\(_x\)Te-HgTe superlattices have been systematically investigated. Several narrow well widths were chosen, e.g., 30, 35 and 40 Å, and the barrier widths were varied between 24 and 90 Å for a particular well width. Both the well width and the total period were determined directly by means of x-ray diffraction. The well width was determined by exploiting the high reflectivity from HgTe and the low reflectivity from CdTe for the (002) Bragg reflection. Knowing the well and barrier widths we have been able to set an upper limit on the average Cd concentration of the barriers, \(\overline x_b\), by annealing several superlattices and then measuring the composition of the resulting alloy. \(\overline x_b\) was shown to decrease exponentially with decreasing barrier width. The structure of a very short period superlattice, i.e., 31.4 Å, was also investigated by transmission electron microscopy, corroborating the x-ray diffraction results. Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37858 ER - TY - JOUR A1 - Wu, Y. S. A1 - Becker, Charles R. A1 - Waag, A. A1 - Bicknell-Tassius, R. N. A1 - Landwehr, G. T1 - The effects of laser illumination and high energy electrons on molecular-beam epitaxial growth of CdTe N2 - We report the results of a detailed investigation on the Te-stabilized (2 x 1) and the Cdstabilized c( 2 X 2) surfaces of ( 100) CdTe substrates. The investigation demonstrates for the first time that both laser illumination and, to a greater extent, high-energy electron irradiation increase the Te desorption and reduce the Cd desorption from ( 100) CdTe surfaces. Thus it is possible by choosing the proper growth temperature and photon or electron fluxes to change the surface reconstruction from the normally Te-stabilized to a Cd-stabilized phase. Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30795 ER - TY - JOUR A1 - Wu, Y.S. A1 - Becker, Charles R. A1 - Waag, A. A1 - Kraus, M. M. A1 - Bicknell-Tassius, R. N. A1 - Landwehr, G. T1 - Correlation of the Cd-to-Te ratio on CdTe surfaces with the surface structure N2 - We report here that reconstruction on (100), (1lIlA, and (1l1lB CdTe surfaces is either C(2X2), (2X2), and (l X I) or (2X I), (l X I), and (l X I) when they are Cd or Te stabilized, respectively. There is a mixed region between Cd and Te stabilization in which the reflected high-energy electron-diffraction (RHEED) patterns contain characteristics of both Cd- and Te-stabilized surfaces. We have also found that the Cd-to-Te ratio of the x-ray photoelectron intensities of their 3d\(_{3/ 2}\) core levels is about 20% larger for a Cd-stabilized (1lIlA, (1lIlB, or (100) CdTe surface than for a Te-stabilized one. According to a simple model calculation, which was normalized by means of the photoelectron intensity ratio of a Cd-stabilized (lll)A and aTe-stabilized (1l1lB CdTe surface, the experimental data for CdTe surfaces can be explained by a linear dependence of the photoelectron-intensity ratio on the fraction of Cd in the uppermost monatomic layer. This surface composition can be correlated with the surface structure, i.e., the corresponding RHEED patterns. This correlation can in turn be employed to determine Te and Cd evaporation rates. The Te reevaporation rate is increasingly slower for the Te-stabilized (Ill) A, (l1l)B, and (100) surfaces, while the opposite is true for Cd from Cd-stabilized (Ill) A and (Ill)B surfaces. In addition, Te is much more easily evaporated from all the investigated surfaces than is Cd, if the substrate is kept at normal molecular-beam-epitaxy growth temperatures ranging from 2oo·C to 300 ·C. KW - Festkörperphysik Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37789 SN - 0163-1829 ER -