|Title||Microstructure of Ti/Al/Ni/Au ohmic contacts for N-polar GaN/AlGaN high electron mobility transistor devices|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Zhou, L, Johnson, MR, Smith, DJ, Meyer, DJ, Storm, DF, Katzer, DS, Downey, BP|
|Type of Article||Article|
|Keywords||gan, hemts, layer, ti/al|
The microstructure of Ti/Al/Ni/Au ohmic contacts on N-polar GaN/AlGaN high electron mobility transistor heterostructures annealed from 800 degrees C to 900 degrees C has been studied using transmission electron microscopy and associated analytical techniques. Two ohmic metal stacks with different Ti/Al/Ni/Au layer thicknesses (20/200/40/50 nm and 20/100/10/50 nm) have been examined. Samples with low ohmic contact resistance after annealing were found to have two common characteristics: (1) the top GaN channel layer had completely reacted with Ti metal to form a polycrystalline TiN layer and (2) a similar to 5 nm-thick Au-rich layer was present near the TiN/AlGaN interface. Possible conduction mechanisms related to the presence of Au in low ohmic contact resistance samples are discussed. (C) 2014 American Vacuum Society.
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