Potential imaging of operating light-emitting devices using Kelvin force microscopy

Abstract

We report on the measurements of two-dimensional potential distribution with nanometer spatial resolution of operating light-emitting diodes. By measuring the contact potential difference between an atomic force microscope tip and the cleaved surface of the light emitting diode, we were able to measure the device potential distribution under different applied external bias. It is shown that the junction built-in voltage at the surface decreases with increasing applied forward bias up to flatband conditions, and then inverted. It is found that the potential distribution is governed by self-absorption of the sub-band-gap diode emission.

Microscopic surface photovoltage spectroscopy

“…Such images have been analyzed by us in detail in the past. 9 In ideal ͑surface states free͒ cleaved structures, the region with the higher CPD is the p side of the junction since it has a higher work function than the n side. However, in Fig.…”

Kelvin probe measurements of microcrystalline silicon on a nanometer scale using SFM

“…To prevent the problems with the reverse polarized p−Si/n−TCO diode experiments on reverse stacking of the doped layers will be done. Future investigations will be carried out with illumination and diode bias voltages in order to extend the results to photovoltaic generator conditions [4,5].…”

Local measurement of surface states energy distribution in semiconductors using Kelvin probe force microscope

“…The KPFM measurements were conducted using a commercial atomic force microscope ͑Autoprobe CP, Veeco, Inc.͒ operating in the a͒ Electronic mail: yossir@eng.tau.ac.il noncontact mode. The KPFM measurements ͑based on a setup described previously 13 ͒ were conducted inside a nitrogen containing ͑Ͻ2 ppm relative humidity͒ glove box.…”