Defects and Self-Compensation in Semiconductors

Abstract

Defect formation and doping limits in semiconductors are discussed in terms of the amphoteric defect model (ADM). It is shown that the nature of defects, acceptor-like or donor-like, depends on the location of the Fermi energy relative to a common energy reference, the Fermi level-stabilization energy. The maximum free electron or hole concentration that can be achieved by doping is an intrinsic property of a given semiconductor and is fully determined by the location of the semiconductor band edges with respect to the same energy reference. The ADM provides a simple phenomenological rule that explains experimentally observed trends in free carrier saturation in a variety of semiconductor materials and their alloys. The predictions of a large enhancement of the maximum electron concentration in III-N-V alloys have been recently confirmed by experiment.

Review—Dopant Selection Considerations and Equilibrium Thermal Processing Limits for n+-In0.53Ga0.47As

“…The amphoteric native defect model proposed by Walukiewicz [87][88][89] and experimental DFT calculations suggest that with heavy n-type doping the Fermi level shifts toward the conduction band and there is a resultant decrease in the enthalpy of formation for negatively charged V III . 75,90,91 The formation energy of these defects is dependent on the background electrical characteristics such that any dopant species which can cause the requisite Fermi level shift would result in lowering of the formation energy of vacancies.…”

“…111 Dopant-defect complexing seems to provide the best explanation of the observed equilibrium electrical activation limits 89,[112][113][114][115] and diffusion phenomenon in n-InGaAs substrates and there is a large body of experimental evidence suggesting that high vacancy concentrations exist in heavily n-type GaAs substrates.…”

Wide-Gap Chalcopyrites

“…Thus, more donors will form increasing the degree of compensation. Such a behavior can be described by the Fermi-level stabilization model [127][128][129] and is usually observed as an off-leveling of charge carrier concentration with increasing dopant concentration or by the fact that semiconductors can be doped only p-type or n-type [130,131]. The effect has been observed till now as the self-compensation of extrinsic dopants by native defects.…”

Guilty as Charged: The Role of Undercoordinated Indium in Electron-Charged Indium Phosphide Quantum Dots

“…Possibly present trap states in the bandgap would also simply be filled or emptied upon doping. However, it is well known that charging of semiconductors can result in the formation of charge-compensating defects . For semiconductor nanocrystals such defects most likely appear on the surface in the form of local reduction/oxidation of surface atoms or the formation of dimers .…”

“…However, it is well known that charging of semiconductors can result in the formation of charge-compensating defects. 28 For semiconductor nanocrystals such defects most likely appear on the surface in the form of local reduction/oxidation of surface atoms or the formation of dimers. 29 For example, Du Fosséet al showed in a computational study that Cd-based QDs without dangling bonds are stable up to a charge of one electron but form trap states after injection of more electrons.…”