4 December 2012 Optical resistance of GaN and InGaN thin films
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Abstract
Group III nitrides are wide band-gap semiconductors which are commonly used in high power and high frequency electronics and optoelectronics. A rapid development of GaN/InGaN devices is in progress however many technological improvements are still demanded. One of them is a convenient formation of electrical contacts attached to appropriate layers. Currently a selective etching step of GaN and InGaN layers is performed by using quite expensive methods such as plasma, chemical-lithographic or electron beam exposure. However, very little research has been done towards investigation of an alternative selective laser etching possibility. Therefore in this work we study optical resistance and damage morphology of thin film GaN and InxGa1-xN layers grown on sapphire substrates in the femtosecond regime. Laser induced damage threshold (LIDT) tests were carried out in both S-on-1 and 1-on-1 regimes by exposing samples from front (deposited) and rear (substrate) sides. For optical resistance testing a femtosecond Yb:KGW laser combined with harmonic generator covering near IR spectrum to visible and UV was used. Experimental results of optical resistance dependence on band-gap in InxGa1-xN layers with different indium concentration (X up to 22%) are presented. Also detailed morphology study for different laser wavelengths is performed and discussed.
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Mindaugas Ščiuka, Mantas Dmukauskas, Tomas Grinys, Andrius Melninkaitis, "Optical resistance of GaN and InGaN thin films", Proc. SPIE 8530, Laser-Induced Damage in Optical Materials: 2012, 85300Y (4 December 2012); doi: 10.1117/12.977451; https://doi.org/10.1117/12.977451
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