C. Grattepain

Indium doping of CdTe layers and CdTe/Cd1 − xZnxTe microstructures

Abstract Doping of CdTe and Cd 1 − x Zn x Te layers and heterostructures with indium donors during their growth by MBE is described. Characterization by SIMS, electrical measurements and photoluminescence is presented with emphasis on: activation efficiency for uniform and planar doping; degree of localization achieved for step-like doping profiles; doped single and multiple quantum wells. Compensation by acceptor impurities and by intrinsic defects occurs at low (≈ 10 16 cm -3 ) and at high ( 18 cm -3 ) In concentrations, respectively. Essentially 100% activation efficiency of the donors is achieved in the intermediate range.

Annealing kinetics of hydrogenated As acceptors in MOVPE grown CdTe

The kinetics of electrical activation of hydrogenated arsenic acceptors in MOVPE grown cadmium telluride layers was studied for arsenic doping in the range to . Thermal annealings were performed in the temperature interval 150-C with a duration from 1 s to 1 h. The hole concentration in the annealed samples was determined by the van der Pauw method and As-H pair concentration was deduced from the intensity of the LVM absorption line at , detected by Fourier transform spectrometry. Short annealing experiments (<1 min) showed a continuous increase in hole concentration with time and temperature, limited to about (1- at a temperature of C. The concentration of As-H pairs concurrently decreased but at a higher rate. Longer annealings usually led to a decrease in hole concentration while the As-H pair concentration either continued to drop or recovered depending on the value of arsenic doping. These results were interpreted in the framework of a theoretical analysis which took into account several processes: dissociation-recombination of impurity-hydrogen pairs, electronic ionization of arsenic impurities and electrical compensation due to the formation of arsenic-vacancy complexes. It was proposed that arsenic ionization takes place in two steps, the first one corresponding to a thermally activated conversion process and the second one to hole emission. The microscopic nature of the intermediary neutral impurity state is not known at present.

Investigation of hydrogen, carbon and further impurities in the metalorganic vapour phase epitaxy of ZnSe with ditertiarybutylselenide and methylallylselenide

Abstract The impurities in ZnSe layers grown by metalorganic vapour phase epitaxy (MOVPE) on (001) GaAs have been investigated by photoluminescence (PL) and secondary ion mass spectrometry (SIMS) measurements. The layers grown with the alkyl combination methylallylselenide/diethylzinc (MASe/DEZn) exhibit the incorporation of C and H detected by SIMS. The use of helium instead of the hydrogen carrier gas increases the incorporation of C and H. At very high concentrations (H ≈ 10 20 cm -3 ) a new PL peak at 2.786 eV appeared. The mass spectroscopic investigation of the pyrolysis of MASe revealed a simple bound cleavage as the dominant mechanism which generates the intermediate species SeCH 3 . The following extrinsic impurities were found in the layers: (1) Cu from the growth system (PL, SIMS); (2) halogen (Br and I) from the Se source (PL, synthesis, SIMS); (3) oxygen from the system or carrier gas (SIMS); (4) Te from former ZnTe growth (SIMS); (5) As and Ga from the substrate (SIMS). The layers grown with the alkyl combination ditertiarybutylselenide/dimethylzinc-triethylamine (DTBSe/DMZn-TEN) show weak contaminations by C and H as detected by SIMS. The mass-spectroscopic investigation of the pyrolysis of DTBSe revealed H 2 Se and elemental Se as products from parallel mechanisms. The volatile alkyls isobutane and isobutene are found as reaction products. The role of the Zn alkyl as the source of the C and H incorporation is not yet clarified. The following extrinsic impurities were found in the layers: (1) Cu from the growth system (SIMS); (2) either Al or Cl as a donor (PL); (3) O from the system or carrier gas (SIMS); (4) S possibly from substrate preparation (SIMS); (5) As and Ga from the substrate (PL, SIMS). However, the layer purity is already sufficient for first doping experiments. With P doping, a hole concentration of 10 15 cm -3 is achieved.

Impurity incorporation during epitaxial growth of GaAs by chemical reaction

Vapour-phase epitaxy of GaAs in conditions where the growth is limited by the chemical reactions of the gases with the substrate and not by gas transport is correctly understood in case the gases are produced by the decomposition of a GaAs source by H 2 O. Using secondary ion mass spectroscopy we have measured the e

Low temperature growth of (Cd,Hg) Te layers by MOVPE

ciency at which various impurities (C, O, Si, S, Zn, Mg, Cr and Fe) are transported from the source into the grown layer. It is found that impurity transport is driven by the formation of volatile oxides, allowing to foresee which impurity can or cannot be incorporated into the grown layer. ( 2000 Elsevier Science B.V. All rights reserved.

Twin-free CdHgTe layers grown by MOCVD on vicinal (211) GaAs surfaces

Abstract MCT layers have been grown for the first time at 250°C using DATe, DMCd and mercury. First the buffer layer CdTe grown at 365°C using DIPTe and DMCd is studied with an emphasis on the influence of the substrate orientation. Indeed the surface morphology and the crystalline quality may change dramatically as a function of the substrate orientation. Then the low temperature MOVPE growth of (Cd,Hg)Te is described: different compositions were achieved and the crystalline and electronic properties are presented.

Donor activation efficiency and doping profile quality in In-doped CdTe and CdZnTe quantum structures

Abstract Following a study on the morphological and structural properties of CdTe and CdZnTe layers grown by MOCVD on GaAs substrates of ( h 11) orientation and A or B polarity, the growth on (211) GaAs substrates misoriented toward (111) and (100) is investigated. High structural quality twin-free CdHgTe layers of near (525) orientation are obtained on (211) surfaces misoriented toward (111), while a misorientation toward (100) leads to a very high density of twins. These results are explained from the bond features at the growth interface.

Influence of a ZnMnTe nucleation layer on the structural quality of (111) ZnTe grown by MOVPE on (100) GaAs

Abstract In-doping of CdTe and Cd 1−x Zn x Te ( x ) layers and quantum structures is performed during molecular beam epitaxy with a Cd overpressure. The In flux is determined as a function of the cell temperature. The role of the Cd overpressure in the activation efficiency is studied. Carrier mobilities of up to 5300 cm2 V−1 s−1 are observed at light doping levels. In migration and formation of In-related compounds are studied by X-ray photoelectron spectroscopy. The doping profile quality is studied by secondary ion mass spectroscopy: efficient, well localized doping is achieved for low growth temperatures (200–220°C) and low sheet densities (about 1011 cm−2); otherwise marked migration of the dopant is observed.

Novel modulated flow technique for the OMCVD growth of CdHgTe at 300°C

The improvement of a ZnTe surface layer quality is reported. For the first time a ZnTe layer of (111) orientation has been grown on (100) GaAs substrate. This orientation, which is responsible for high layer quality, was induced when adding Mn at the onset of the ZnTe growth. This leads to a ZnMnTe nucleation layer responsible for the high morphology quality of the layer.

n- And p-type modulation doping of Te related semimagnetic II–VI heterostructures

Abstract A new growth process, called vapour interdiffusion process (VIP), intermediate between interdiffusion multilayer process (IMP) and atomic layer epitaxy (ALE), has been investigated to produce homogeneous CdxHg1−xTe layers by OMCVD at 300°C. Experimental conditions such as flow rate, partial pressures and II VI ratio have been previously optimized to grow CdTe and HgTe at this temperature. Compared to direct alloy growth (DAG) and IMP, VIP is shown to give better surface morphology and crystallographic quality of the layers. Sample quality was characterised by X-ray double diffraction and photoluminescence while surface morphology was assessed by scanning electron microscopy (SEM).