Depth and thermal stability of dry etch damage in GaN Schottky diodes

Abstract

GaN Schottky diodes were exposed to N2 or H2 Inductively Coupled Plasmas prior to deposition of the rectifying contact. Subsequent annealing, wet photochemical etching or (NH&S surface passivation treatments were examined for their effect on diode currentvoltage characteristics. We found that either annealing at 750 'C under N2, or removal of -500-600 A of the surface essentially restored the initial I-V characteristics. There was no measurable improvement in the plasma-exposed diode behavior with (NH&S treatments. 1 DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document.GaN-based devices are being developed for two basic classes of applications, namely blue/green/UV emitters and high power/high temperature electr~nics.(''~) The high bond energy, 8.92 eV/atom, of GaN has necessitated use of dry etching technologies for device patterning. Plasma induced damage to GaN may take several forms, all of which lead to changes in its electrical and optical properties, as follows:1. Ion induced creation of lattice defects which generally behave as deep level states and thus produce compensation, trapping or recombination in the material. Due to channeling of the low energy ions that strike the sample, and rapid diffusion of the defects created, the effects can be measured as deep as 1000 surface, even though the projected range of the ions is only 110 A. to 10l8 cme3. In the PL spectrum an intense broad band appeared at 3.05 eV, and there was an increase in intensity of the yellow band at 2.20 eV. The latter is thought to involve defects such as Ga, in some models. Use of Ar+/N2+ ion beams produced less degradation of both optical and electrical properties.Saotome at studied the effects of RIBEECR etching with pure Cl2 on GaN properties. Etch rates up to -1000 A-min-' at 500 V beam voltage were obtained. He-Cd (325 nm) laser irradiation was used to measure PL from RlBE GaN samples before and after photo-assisted wet etching in an 85% KOH:H20 (1:3) solution. The RIBE treatment decreased near band-edge PL intensity by a factor of approximately five, whereas subs...

Observation of inductively coupled-plasma-induced damage on n-type GaN using deep-level transient spectroscopy

“…Inductively coupled plasma ͑ICP͒ etching of GaN led to severe degradations of the Schottky contact, the decrease of Schottky barrier height, and the increase of reverse leakage current by several orders of magnitudes. 4 Deep-level transient spectroscopy ͑DLTS͒ is an effective tool in obtaining information about traps in semiconductors. In particular, the depth distribution of deep levels is easily obtained, which is critical in interpreting the electrical properties of the devices.…”

Doping level-dependent dry-etch damage in n-type GaN

“…Figure 3(a) shows typical I-V characteristics of the Schottky diodes on the HDG sample. The diodes were leaky when the sample was etched at 100 W and 200 W of rf power due to the collective effects of etch-induced damage [11,12], while the NPT showed a decrease in leakage current for 100 W etched samples, especially in the reverse current region (not shown). This indicates that NPT treatment is an effective method for recovering the stoichiometry of the nitrogen deficient surface, consistent with the result of Figs.…”

“…The specific contact resistivity (ρ c ) and current-voltage (I-V) measurement, extracted from the ohmic contact and Schottky diodes, respectively, have been found to be very sensitive to surface damage induced by the dry-etching of semiconductors [8]. Although the effects of the ion bombardment of non-reactive gases in the plasma have been reported by exploiting a metal-semiconductor contact method [9][10][11][12], only a few results have been reported on the electrical characterization of dry-etched GaN under a actual device fabricating conditions. It is known that the depth of the damaged surface, etched with a chemical component, should be smaller than those etched using a physical component [12].…”

Photoluminescence recovery by in-situ exposure of plasma-damaged n-GaN to atomic hydrogen at room temperature

“…Cao et al have found that rapid thermal annealing of plasmaetched GaN recovers its electrical properties as demonstrated by the current-voltage characteristics of Schottky diodes. 12 High-temperature annealing might, however, lead to the preferential removal of N atoms from the GaN surfaces. Lee et al have reported that N 2 plasma treatment improves the photoluminescence (PL) characteristics of heavily damaged GaN surfaces.…”