Depletion region

About: Depletion region is a research topic. Over the lifetime, 9393 publications have been published within this topic receiving 145633 citations.

(GaAl)As‐GaAs heterojunction transistors with high injection efficiency

Abstract: n (GaAl)As‐pGaAs‐nGaAs heterojunction transistors were fabricated by the liquid‐phase epitaxial technique, where two kinds of etchants were used to expose the pGaAs base region. The characteristics of the heterojunction transistors are examined as functions of the injection current density and the temperature. Electrical measurements showed that the transistors have a common emitter current gain β of up to 350. The defect current component in the emitter heterojunction is the recombination current in the depletion region.

Tuned NV emission by in-plane Al-Schottky junctions on hydrogen terminated diamond

Abstract: The negatively charged nitrogen-vacancy (NV) centre exhibits outstanding optical and spin properties and thus is very attractive for applications in quantum optics. Up to now an active control of the charge state of near-surface NV centres is difficult and the centres switch in an uncontrolled way between different charge states. In this work, we demonstrate an active control of the charge state of NV centres (implanted 7 nm below the surface) by using an in-plane Schottky diode geometry from aluminium on hydrogen terminated diamond in combination with confocal micro-photoluminescence measurements. The partial quenching of NV-photoluminescence caused by the hole accumulation layer of the hydrogen terminated surface can be recovered by applying reverse bias potentials on this diode, i.e. the NV0 charge state is depleted while the NV− charge state is populated. This charge state conversion is caused by the bias voltage affected modulation of the band bending in the depletion region which shifts the Fermi level across the NV charge transition levels.

Optically-controlled ion-implanted GaAs MESFET characteristic with opaque gate

Abstract: An analytical modelling has been carried out for an ion-implanted GaAs MESFET having a Schottky gate opaque to incident radiation. The radiation is absorbed in the device through the spacings of source, gate, and drain unlike the other model where gate is transparent/semitransparent. Continuity equations have been solved for the excess carriers generated in the neutral active region, the extended gate depletion region and the depletion region of active (n) and substrate (p) junction. The photovoltage across the channel and the p-layer junction and that across the Schottky junction due to generation in the arc region of the gate depletion layer are the two important controlling parameters. The I-V characteristics and the transconductance of the device have been evaluated and discussed.

New findings of X-ray energy responses of silicon surface barrier detectors and their generalized theoretical extension to X-ray responses of position sensitive detectors

Abstract: X-ray energy responses of silicon surface barrier (SSB) semiconductor detectors are found to be explained neither by the commonly believed conventional model using the depletion layer thickness of an SSB detector nor by a recently proposed model using its wafer thickness as the X-ray sensitive layer Our new theory using both the depletion layer sensitivity and the X-ray response due to a three-dimensional charge diffusion effect in the field-free substrate region of a SSB detector can well fit the response data This theory is newly extended to analyse each channel response of a multichannel semiconductor X-ray detector fabricated on one silicon wafer; these detectors are widely utilized as position sensitive X-ray detectors for nuclear fusion oriented plasma research as well as for high energy elementary particle studies A numerical simulation of multichannel detector outputs using our three dimensional diffusion theory is carried out; generalised theoretical formulae are also presented

The superposition principle for homojunction solar cells

Abstract: The superposition principle for solar cells states that the current flowing in an illuminated cell subject to a forward bias V is given by the algebraic sum of the short-circuit photocurrent and the current which would flow at bias V in the dark. Several authors have published arguments establishing the validity of this principle for homojunction cells operated so that the minority-carrier concentrations in the quasi-neutral regions do not exceed low injection levels. All these arguments depend on the assumption that the quasi-Fermi levels are constant across the depletion region of a forward-biased, illuminated cell. The accuracy of this assumption is examined in detail in the present paper. It is found that the quasi-Fermi levels do, in fact, vary significantly across the depletion region of an illuminated cell operated at short-circuit or low forward bias. However, it is shown that if the carrier mobilities are reasonably high and the carrier lifetimes reasonably long, the superposition principle still provides an excellent description of the cell characteristics at all bias levels. The superposition principle may seriously overestimate the efficiency of cells fabricated on poor-quality substrates with very short lifetimes and low mobilities.