Coupled Defect Level Recombination in the P—N Junction

Abstract

The well known Shockley-Read-Hall (SRH) model considers emission and capture processes at defects exhibiting a single level or multiple non-coupled levels in the band gap of the semiconductor. The present paper generalizes the model to the case of two mutually coupled defect levels acting as trapping centres. If the intercenter transition is not considered, the model reduces to the case of two non-coupled levels treated by the SRH model. THEORYThe paper considers the existence of lattice defects (electrically active traps) having two coupled defect levels (CDL) in the band gap of the semiconductor between which thermal exchange of free charge carriers takes place. The two coupled capture centres are denoted by indices a and b with corresponding energies E Our CDL model considers ten exchange processes of free charge carriers between the capture centres and the conduction and valence bands. These processes are schematically shown in Fig. 1.Each of the ten exchange processes (five capture and five emission processes) is characterized by its escape time. If the unknown occupation probability of a trapping centre is divided by the escape time of a capture process, or the probability of non-occupation by the escape time of an emission process, one obtains the frequency of the particular exchange process. The frequencies of exchange processes allow to build two equations with two unknown variables, the occupation probabilities of centres a and b. Their solution leads to a quadratic equation yielding finally the occupation probabilities. Then, in terms of the ten escape times and of the evaluated occupation probabilities of centres a and b one can correctly define the SRH and CDL recombination rates contained in the continuity equations [3]. The quasi-static continuity equations for electrons and holes can be written as 1 q dJ e

Efficient Band-to-Trap Tunneling Model Including Heterojunction Band Offset

“…Once the normalization factor N is known, the 3D DOS can be immediately calculated using Eq. [7], and so the field enhancement factor is readily computed according to Eq. [2].…”

“…This factor can become very large under high electric fields, and consequently significantly reduce the lifetime. The three major models used to compute the field enhancement factor are the Schenk model (2,5), the Hurkx model (6), and the Racko model (7), with the first two being commonly available in commercial TCAD device simulation tools (8). These models may be sufficient for modeling band-to-trap tunneling processes in homojunction devices.…”

The Impact of Successive Gamma and Neutron Irradiation on Characteristics of PIN Photodiodes and Phototransistors

“…The enhancement of the generation rate arises because the large transition from the valence band to the above midgap level is mediated by the donor level. This shortens the time taken for the upper state to become filled and hence increases its fractional occupancy [12,38]. The enhancement of the fractional occupancy increases the number of electrons generated per unit of time from a defect state and hence increases the photocurrent [33].…”