Dopant Electromigration in Semiconductors

Abstract

A doped semiconductor can be viewed as a mixed electronic-ionic conductor, with the dopants as mobile ions. Normally the temperature range where this becomes true is not even close to that where the (0pto)electronic properties of the material are of interest. However, notable exceptions exist and these are reviewed here, with special emphasis on those cases where semiconductivity is preserved when the (mobile) dopant concentration changes and ambipolar behavior can be obtained by dopant mobility. Dopant diffusion and drift are of interest not only in materials such as Si:Li, known from its use in radiation detectors, but also in other semiconductors, ranging from 11-VIs and related compounds, such as (Hg,Cd)Te and CuInSe2 to Ill-Vs and potential high temperature semiconductors, such as diamond. Better understanding of the phenomena is important also because of the implications that it has for device miniaturization, as dopant diffusion and drift put chemical limits to device stability. Such understanding can also make dopant electromigration useful for low-temperature doping. Some basic theory for electric-field-induced dopant migration is given and compared to experiments.

Synchrotron X-ray Diffraction Evidence for Native Defects in the Photovoltaic Semiconductor CuInSe2

“…Our results provide clear experimental indication (in addition to radioactive tracer studies [4] ) for the thermally-assisted electromigration mechanism that has been proposed for E-field induced transistor formation. They provide important experimental support for the model of ion migration-mediated self-stabilization of CuInSe 2 -based solar cells.…”

“…It has been shown that application of a strong E-field to CuInSe 2 crystals can change the electrical conductivity type of this semiconductor material. [3] This behavior has been explained by thermally assisted electromigration of Cu, [4,5] consistent with radioactive 64 Cu tracer experiments. [6] Electromigration of Cu has also been invoked to explain the remarkable stability of solar cells made with the material.…”

Copper Indium Selenides and Related Materials for Photovoltaic Devices

“…351,363 Some theoretical models propose that this relaxation results from the redistribution of ionized copper atoms in the space-charge region under the influence of the modified internal electric field of the diode when there is photogenerated current. 363,369 The application of spectral methods of electrooptical characterization to the study of these transient processes in CIGS strongly suggest that multiple mechanisms are involved. 370,371 These phenomena remain an active area of current research.…”

Nanoscale p-n junction fabrication in silicon due to controlled dopant electromigration

“…4 As a result, a degradation of an electric field-induced structure slows down. 10 Additional experiments are required to understand the mechanism of nano-p-n junction annihilation.…”