Optical admittance spectroscopy: A new method for deep level characterization

Abstract

A new method for the optical cross-section measurement of deep levels in junctions is presented. It is based on the measurement of the capacitance and conductance of the junction under illumination, as a function of the photon energy hν and the frequency of the measuring signal. This technique has been applied to the measurement of the optical capture cross section σon of the Au acceptor level corresponding to the emission of electrons to the conduction band.

Observations of deep levels in 4H-SiC using optoelectronic modulation spectroscopy

“…Table I summarizes the states that have been observed in this work and compares them with trap levels measured previously 9,10 using optical admittance spectroscopy 11 and with DLOS observations. The range from 2.3 eV to 2.9 eV encompasses a broad contra-phase range of response indicating a range of unresolved hole states in this energy range.…”

“…A very useful basis for comparison is provided by previous work on 6H-SiC 8 and 4H-SiC 9,10 using optical admittance spectroscopy 11 and with DLOS. The method used is optoelectronic modulation spectroscopy 6,7 which can reveal the optical transition energy, whether the state is a hole or an electron trap and provide an indication of its extent of localization.…”

Characterization of electronic states in molecular beam epitaxy grown GaN by optical admittance spectroscopy: Comparison of different nitrogen plasma sources

“…5 The latter technique allows the determination of the optical threshold energy and the spectral dependence of the capture cross section of deep states to quantitatively describe deep level-to-band transitions. 6 It has been successfully applied especially to high resistivity 6H-SiC. 7 The goal of this work is not only the characterization of deep and shallow states in GaN grown by molecular beam epitaxy ͑MBE͒, but a systematic comparative study of layers grown with different nitrogen plasma sources to estimate the influence of the used source on the layer properties.…”

Kinetics of slow buildup of photoconductance in n-type 6H–SiC

“…The details of this measuring technique have been described elsewhere. [9][10][11] Four nitrogen doped silicon carbide specimens ͑w1, w2, w3, and w4͒ used for these studies were obtained from two different crystal growers using the physical vapor transport ͑PVT͒ growth method. Sample preparation ͑polishing, cleaning, and oxidation͒ and diode fabrication have been described elsewhere.…”