L. Dobaczewski

LAPLACE-TRANSFORM DEEP-LEVEL TRANSIENT SPECTROSCOPY STUDIES OF THE G4 GOLD-HYDROGEN COMPLEX IN SILICON

We have studied n-type silicon containing gold and gold–hydrogen complexes using high-resolution “Laplace” deep-level transient spectroscopy. This technique has enabled two quite distinct electron emission rates to be observed at temperatures between 240 and 300 K. These are associated with the gold acceptor and the level referred to as G4, which is observed when hydrogen and gold are present in silicon. The gold acceptor has a measured activation energy for electron emission of 558±8 meV, and the G4 state of 542±8 meV. The directly measured electron capture cross section for G4 is determined to be 0.6±0.1 σn(gold acceptor) at 275 K from which it is inferred that the state is acceptor-like.

Properties of epitaxially grown CdTe layers doped with indium

Abstract We report on the growth and characterization of n-type indium-doped CdTe films grown by molecular beam epitaxy on GaAs substrates. By varying the In flux we are able to control the carrier concentration in the range from 8 × 1014 to 1.5 × 1018 cm−3. The samples have been investigated by photoluminescence, transport, and deep level transient spectroscopy (DLTS) measurements. By DLTS we established that the concentration of the dominant electron trap, located at 0.45 eV below the edge of the conduction band, is proportional to the net donor concentration. This result indicates that the trap may be related to the presence of indium dopants.

Spectroscopic studies of iron and chromium in germanium

We report on the electronic properties of Fe and Cr in n-type germanium studied using conventional and Laplace Deep Level Transient Spectroscopy techniques (LDLTS). Using Schottky barriers restricts the studies to levels located in the upper half of the band gap. However, by applying external optical excitation to generate minority carriers, the investigation is extended to the lower half of the band gap. Major findings already published by other authors are in several cases confirmed. However, new insight is revealed on the microscopic behavior of these two chemical species such as their interactions with hydrogen giving rise to the generation of complex-related levels in the band gap. For the Fe case, the small difference in energy of its two levels raises the question as to the possibility of negative-U character.

Understanding ion implantation defects in germanium

The recent interest in germanium as an alternative channel material for PMOS has revealed major differences from silicon in relation to ion implantation. In this paper we describe some initial results of a fundamental study into defect creation and removal in ion implanted germanium. In this stage of the work we have used silicon and germanium implants into germanium and into germanium rich silicon-germanium. The defect evolution in these samples is compared with electron and neutron irradiated material using annealing studies in conjunction with deep level transient spectroscopy, positron annihilation and Rutherford back scattering. It is proposed that both vacancy and interstitial clustering are important mechanisms in implanted germanium and the likely significance of this is discussed. copyright The Electrochemical Society.

Deep levels governing the transport mechanism in p-n HgMnTe diodes

Preliminary results of DLTS studies on Hg1-xMnxTe (x=0.18, 0.20) are presented. One dominant majority carrier trap on the p-type side of the diodes was observed. Its concentration, hole capture cross-section, and the activation energy for thermal emission were found to be equal to 5X1016 cm-3, 10-17 cm2, and 110 meV, respectively. A strong dependence of defect occupancy on the number of electrons injected into the space charge region allowed us to identify these deffects as very effective recombination centers limiting the device performance.

Deep level transient spectroscopy of hole traps related to CdTe self‐assembled quantum dots embedded in ZnTe matrix

The capacitance—voltage (C‐V) and deep level transient spectroscopy (DLTS) measurements have been performed on a Schottky structure containing self‐assembled CdTe quantum dots (QDs) embedded in ZnTe (p‐type) matrix. A characteristic step on the C‐V curve due to charge accumulation on QD states as well as QD related DLTS signal were found. Thermal activation energy of 0.1 eV was obtained from Arrhenius plot related to the signal. This energy level can be related either to the hole emission from the defects accompanying QD formation or to the hole emission from the QD states to the ZnTe valence band.

Formation of the DX State by Donors in Al_{x}Ga_{1-x}As - Experiment

The fundamental problem related to the properties of DX centres is understanding the mechanism for the metastability of these defects. Since the early work of Lang [1] this has been thought to be due to the large lattice relaxation (LLR) following electron capture by the DX state. However, the problem of the microscopic stucture of these centres, namely the type or symmetry of the lattice relaxation, is less certain. The computations of Chadi and Chang [2], and Morgan [3], suggest that a substitutional-interstitial defect reaction may be responsible for LLR phenomena. In the present study experimental evidence is presented which can only be interpreted in terms of substitutional-interstitial defect motion being responsible for the DX state formation. It is based on the detailed observation of the influence of the defect local environment on the electron thermal emission process from DX centres in ΑlxGa1xAs. The direct comparison of this process for the DX centre related to silicon, which can replace gallium or aluminium, with that observed for tellurium, which resides in the arsenic sublattice, allowed us to deduce the configuration of atoms when the centre is in the ground state. Our experiments were possible because of a newly developed Laplace-transform isothermal deep level transient spectroscopy (DLTS) technique [4] which gives orders of magnitude better resolution than the conventional DLTS method and enables the influence of the defect local environment on the electron thermal emission process to be observed in detail. The conventional DLTS spectra taken for both types of samples

Two Charge States of Sulphur in GaSb

Such anomalous effects as metastability and persistent photoconductivity at temperatures below 80 K were found for sulphur in GaSb already in the early seventies [1]. Dmowski et al. [2] gave the explanation for this peculiar behavior based on a large lattice relaxation model. Experimental data in the present work allow to reexamine the previous models and consider the sulphur defect as belonging to the socalled DX centres which, according to recent experimental [3] and theoretical [4] indications, appear to have two charge states and form a negative-U system [5] .