A Damage-Reduced Process Revealed by Photoluminescence in Photoelectrochemical Etching GaN

1999 ◽  
Vol 595 ◽  
Author(s):  
J. M. Hwang ◽  
J. T. Hsieh ◽  
H. L. Hwang ◽  
W. H. Hung
Keyword(s):  
Chemical Etching ◽  
Variable Temperature ◽  
Treatment Method ◽  
Yellow Luminescence ◽  
Etching Technique ◽  
Photoelectrochemical Etching ◽  
Shallow Acceptor ◽  
Novel Technique ◽  
Deep Donor

AbstractPhotoelectrochemical (PEC) etching technique has been proven to be an effective method to etch GaN. Despite its success, investigations on etching-induced damage are still scare. In this work, the damage induced by PEC etching of GaN in KOH electrolyte was studied. Photoluminescence (PL) spectroscopy was used to explore the origin of etching-induced damaged layer. From the variable temperature PL measurements, the origin of etching-induced damage was attributed to be the defect complex of VGa-ON (gallium vacancy bonds to oxygeon on nitrogen antisite). With determination of the defect origin, the electronic transition in the etch damage-related yellow luminescence (YL) band was suggested to be deep donor-like state to shallow-acceptor transition. In addition, a post-treatment method with boiled KOH chemical etching was developed to remove the thin damaged layer. In this method, crystallographic etching characteristics of boiled KOH was observed to assist in the formation of smooth sidewall facets. As revealed by the reduction of yellow luminescence, we propose this novel technique as a near damage-free etching method.

scholarly journals A damage-reduced process revealed by photoluminescence in photoelectrochemical etching GaN

2000 ◽  
Vol 5 (S1) ◽  
pp. 873-879 ◽  
Author(s):  
J. M. Hwang ◽  
J. T. Hsieh ◽  
H. L. Hwang ◽  
W. H. Hung
Keyword(s):  
Chemical Etching ◽  
Variable Temperature ◽  
Treatment Method ◽  
Yellow Luminescence ◽  
Etching Technique ◽  
Photoelectrochemical Etching ◽  
Shallow Acceptor ◽  
Novel Technique ◽  
Deep Donor

Photoelectrochemical (PEC) etching technique has been proven to be an effective method to etch GaN. Despite its success, investigations on etching-induced damage are still scare. In this work, the damage induced by PEC etching of GaN in KOH electrolyte was studied. Photoluminescence (PL) spectroscopy was used to explore the origin of etching-induced damaged layer. From the variable temperature PL measurements, the origin of etching-induced damage was attributed to be the defect complex of VGa-ON (gallium vacancy bonds to oxygeon on nitrogen antisite). With determination of the defect origin, the electronic transition in the etch damage-related yellow luminescence (YL) band was suggested to be deep donor-like state to shallow-acceptor transition. In addition, a post-treatment method with boiled KOH chemical etching was developed to remove the thin damaged layer. In this method, crystallographic etching characteristics of boiled KOH was observed to assist in the formation of smooth sidewall facets. As revealed by the reduction of yellow luminescence, we propose this novel technique as a near damage-free etching method.

Deep Level Related Yellow Luminescence in P-Type GaN Grown by MBE on (0001) Sapphire

1999 ◽  
Vol 595 ◽  
Author(s):  
Giancarlo Salviati ◽  
Nicola Armani ◽  
Carlo Zanotti-Fregonara ◽  
Enos Gombia ◽  
Martin Albrecht ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Deep Level ◽  
Cubic Phase ◽  
Donor Level ◽  
Yellow Luminescence ◽  
Wurtzite Phase ◽  
Shallow Acceptor ◽  
Deep Donor ◽  
P Type ◽  
Deep Donor Level

AbstractYellow luminescence (YL) has been studied in GaN:Mg doped with Mg concentrations ranging from 1019 to 1021 cm−3 by spectral CL (T=5K) and TEM and explained by suggesting that a different mechanism could be responsible for the YL in p-type GaN with respect to that acting in n-type GaN.Transitions at 2.2, 2.8, 3.27, 3.21, and 3.44 eV were found. In addition to the wurtzite phase, TEM showed a different amount of the cubic phase in the samples. Nano tubes with a density of 3×109 cm−2 were also observed by approaching the layer/substrate interface. Besides this, coherent inclusions were found with a diameter in the nm range and a volume fraction of about 1%.The 2.8 eV transition was correlated to a deep level at 600 meV below the conduction band (CB) due to MgGa-VN complexes. The 3.27 eV emission was ascribed to a shallow acceptor at about 170-190 meV above the valence band (VB) due to MgGa.The 2.2 eV yellow band, not present in low doped samples, increased by increasing the Mg concentration. It was ascribed to a transition between a deep donor level at 0.8-1.1 eV below the CB edge due to NGa and the shallow acceptor due to MgGa. This assumption was checked by studying the role of C in Mg compensation. CL spectra from a sample with high C content showed transitions between a C-related 200 meV shallow donor and a deep donor level at about 0.9- 1.1 eV below the CB due to a NGa-VN complex. In our hypothesis this should induce a decrease of the integrated intensity in both the 2.2 and 2.8 eV bands, as actually shown by CL investigations.

scholarly journals Deep level related yellow luminescence in p-type GaN grown by MBE on (0001) sapphire

2000 ◽  
Vol 5 (S1) ◽  
pp. 754-760
Author(s):  
Giancarlo Salviati ◽  
Nicola Armani ◽  
Carlo Zanotti-Fregonara ◽  
Enos Gombia ◽  
Martin Albrecht ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Deep Level ◽  
Cubic Phase ◽  
Donor Level ◽  
Yellow Luminescence ◽  
Wurtzite Phase ◽  
Shallow Acceptor ◽  
Deep Donor ◽  
P Type ◽  
Deep Donor Level

Yellow luminescence (YL) has been studied in GaN:Mg doped with Mg concentrations ranging from 1019 to 1021 cm-3 by spectral CL (T=K) and TEM and explained by suggesting that a different mechanism could be responsible for the YL in p-type GaN with respect to that acting in n-type GaN.Transitions at 2.2, 2.8, 3.27, 3.21, and 3.44 eV were found. In addition to the wurtzite phase, TEM showed a different amount of the cubic phase in the samples. Nano tubes with a density of 3×109 cm−2 were also observed by approaching the layer/substrate interface. Besides this, coherent inclusions were found with a diameter in the nm range and a volume fraction of about 1%.The 2.8 eV transition was correlated to a deep level at 600 meV below the conduction band (CB) due to MgGa-VN complexes. The 3.27 eV emission was ascribed to a shallow acceptor at about 170-190 meV above the valence band (VB) due to MgGa.The 2.2 eV yellow band, not present in low doped samples, increased by increasing the Mg concentration. It was ascribed to a transition between a deep donor level at 0.8-1.1 eV below the CB edge due to NGa and the shallow acceptor due to MgGa. This assumption was checked by studying the role of C in Mg compensation. CL spectra from a sample with high C content showed transitions between a C-related 200 meV shallow donor and a deep donor level at about 0.9-1.1 eV below the CB due to a NGa-VN complex. In our hypothesis this should induce a decrease of the integrated intensity in both the 2.2 and 2.8 eV bands, as actually shown by CL investigations.

Controllable end shape modification of ZnO nano-arrays/rods by a simple wet chemical etching technique

2015 ◽  
Vol 48 (36) ◽  
pp. 365303 ◽  
Author(s):  
Jingchang Sun ◽  
Ting Zhao ◽  
Zhangwei Ma ◽  
Ming Li ◽  
Cheng Chang ◽  
...  
Keyword(s):  
Chemical Etching ◽  
Shape Modification ◽  
Etching Technique ◽  
Wet Chemical ◽  
Wet Chemical Etching

scholarly journals Born out of Fire and Ice: Polymorph Studies of the Antiviral Famciclovir

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 129
Author(s):  
Liana Vella-Zarb ◽  
Ulrich Baisch
Keyword(s):  
Variable Temperature ◽  
Chemical Properties ◽  
Crystal Form ◽  
X Ray Diffraction ◽  
Crystal Forms ◽  
X Ray ◽  
Physical Chemical ◽  
Diffraction Patterns ◽  
Crystalline Forms

There is much interest and focus on solid forms of famciclovir. However, in spite of the abundance of reported differences in oral bioavailability, compressibility, and other physical–chemical properties of the various crystal forms of this drug, very little precise structural analysis is available in the literature to date. The form used in the commercial formulation is the anhydrous form I. Patents and patent applications report three different anhydrous crystalline forms on the basis of unindexed powder diffraction patterns. Single-crystal and variable-temperature X-ray diffraction experiments using the commercially available anhydrous form of famciclovir were carried out and led not only to the crystal structure determination of the anhydrous form I, but also to discovery of a new crystal form of anhydrous famciclovir from powder data.

scholarly journals The Art of Tungsten Etching in Semiconductor Chips

1999 ◽  
Vol 7 (2) ◽  
pp. 24-25
Author(s):  
Lisa Litz-Montanaro
Keyword(s):  
Manufacturing Process ◽  
Chemical Etching ◽  
Layer By Layer ◽  
Ion Milling ◽  
Etching Technique ◽  
Semiconductor Structures ◽  
Wet Chemical ◽  
Wet Chemical Etching ◽  
Semiconductor Chips ◽  
Complex Semiconductor

In the course of both physical and failure analysis of semiconductor chips (i.e., verifying what you actually deposited as a layer, vs, what caused the circuit to fail), it is essential to have appropriate deprocessing tools at your disposal in order to evaluate complex semiconductor structures, Deprocessing techniques are developed for each product manufactured and involve multi-step procedures that reveal the layer-by-layer secrets of the chip, These techniques require constant tweaking in duration and procedure as the manufacturing process imposes changes and as the architecture of the semiconductor changes. While there are many tools that assist in these analytical pursuits, such as RIE (reactive ion etching - a dry etching technique), ion milling, and microcleaving, the wet chemical etching of tungsten is sometimes more reproducible than RIE techniques.

Photoluminescence Excitation Spectroscopy of Carbon-Doped Gallium Nitride

1998 ◽  
Vol 537 ◽  
Author(s):  
E. E. Reuter ◽  
R. Zhang ◽  
T. F. Kuech ◽  
S. G. Bishop
Keyword(s):  
Complete Characterization ◽  
Photoluminescence Excitation ◽  
Yellow Luminescence ◽  
Broad Excitation Band ◽  
Carbon Doped ◽  
Sapphire Substrates ◽  
Red Luminescence ◽  
Unusual Shape

AbstractWe have done a comparative study of carbon-doped GaN and undoped GaN utilizing photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies in order to investigate deep levels involved in yellow luminescence (YL) and red luminescence (RL). When the GaN was excited by above-bandgap light, red luminescence (RL) centered at 1.82 eV was the dominant below-gap PL from undoped GaN, but carbon-doped GaN below-gap PL was dominated by yellow luminescence (YL) centered at 2.2 eV. When exciting PL below the band-gap with 2.4 eV light, undoped GaN had a RL peak centered at 1.5 eV and carbon-doped GaN had a RL peak centered at 1.65 eV. PLE spectra of carbon-doped GaN, detecting at 1.56 eV, exhibited a strong, broad excitation band extending from about 2.1 to 2.8 eV with an unusual shape that may be due to two or more overlapping excitation bands. This RL PLE band was not observed in undoped GaN. We also demonstrate that PL spectra excited by below gap light in GaN films on sapphire substrates are readily contaminated by 1.6-1.8 eV and 2.1-2.5 eV chromium-related emission from the substrate. A complete characterization of the Cr emission and excitation bands for sapphire substrates enables the determination of the excitation and detection wavelengths required to obtain GaN PL and PLE spectra that are free of contributions from substrate emission.

scholarly journals Restoration of Obliterated Stamped Marks on Aluminium Surfaces by Metallographic Etching Technique

2020 ◽  
Vol 36 (6) ◽  
pp. 1212-1217
Author(s):  
Amit Kumar ◽  
Ankit Srivastava ◽  
Tanurup Das ◽  
Abhimanyu Harshey ◽  
Veer Raj Saini ◽  
...  
Keyword(s):  
Forensic Science ◽  
Ferric Chloride ◽  
Present Experiment ◽  
Chemical Etching ◽  
Simple Technique ◽  
Distilled Water ◽  
Metallic Surfaces ◽  
Etching Technique ◽  
Restoration Process ◽  
Science Laboratories

Serial number restoration is a frequently encountered problem in forensic science laboratories for the investigation of theft and burglary cases. These identification marks are generally introduced over metallic surfaces of different vehicle parts and firearms by various means. Chemical etching is one of the most effective and simple technique to restore obliterated, erased, over-stamped and over-engraved marks on metallic surfaces. Several significant studies on restoration of engraved markings on aluminium surfaces were previously reported. The present study attempts to find out an efficient and fast etching reagent to restore obliterated stamped marks on aluminium surfaces. Ten effective etching reagents previously reported by various researchers in their restoration studies were assessed in the present experiment. Etching reagents were individually applied on obliterated surfaces by the cotton swabbing method. The Reagent 3 (ferric chloride 25 g, conc. HCl 25 mL, distilled water 100 mL) was found out to be the most sensitive and rapid (4–6 min) for the restoration on aluminium surfaces. The study also revealed that the absence of an alkaline compound in etching reagent potentially accelerates the speed of the restoration process.

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