Electrochemical Etching and CV-Profiling of GaN

Abstract

We report on the implementation of a robust and reproducible electrochemical CV (ECV) characterization for the (Al, In)GaN material system. A Schottky‐like contact is formed by electrolyte, wetting the area of the semiconductor surface delimited by a sealing ring. In reverse bias with common CV technique the concentration of donors and acceptors can be evaluated. Using a newly developed etch procedure, which we call “cyclic oxidation”, n‐ and p‐type nitrides can be etched (photo‐)electrochemically (PEC) to yield reproducibly etched surfaces with mirror‐like surface morphology at high etch rates (∼3 μm/h). This new etch procedure is explained in detail. The influence of the process parameters on the etch rate is discussed. Using this new etch procedure, various MOVPE and HVPE grown samples have been characterized by CV‐Profiling. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrochemical CV‐profiling of GaN

“…There are successful reports for n-type material if photoelectrochemical (PEC) etching is used instead [3,4], whereas the reports for p-type material in literature are sparse and not very encouraging [5]. We developed a new (photo-) electrochemical etch procedure for nitrides, which we call "cyclic oxidation" and which is described in more detail elsewhere [6]. The cyclic oxidation is based on the observation, that a thin established oxide film is necessary to get smooth etch morphologies [7].…”

“…7a). From SEM studies the surface of the electrochemically etched area with the cyclic oxidation technique is of the same quality as the virgin one [6]. The doping profile in Fig.…”

Electrochemical profiling of heterostructures with multiple quantum wells InGaN/GaN

“…During the standard ECV profiling a nonuniform etching of GaN (or InGaN) surface takes place, leading to a systematic error in the obtained etched area and, hence, in the derived carrier concentration. To prevent this phenomenon the two-stage modification of technique is more preferable: at first stage the oxidation of (In)GaN layer is employed; and at the second stage the etching of the grown oxide takes place [6,7]. In such a way good planarity of etching surface may be obtained.…”

“…By this approach the accuracy and reproducibility of ECV measurements have im-proved. The authors of [6] have demonstrated the ability of profiling GaN substrate on depth to 20 microns with maintenance of a fairly smooth surface.…”

Automated electrochemical CV profiling of LED structures on wafer scale

“…The cyclic oxidation yields mirror-like etched surface morphology for n-and p-type nitride semiconductors [3]. Figure 4.…”