Nonalloyed Ohmic Contacts for HEMTs Using n+-lnGaAs Layers Grown by MOVPE

Mizuhisa NIHEI  Naoki HARA  Haruyoshi SUEHIRO  Shigeru KURODA  

IEICE TRANSACTIONS on Electronics   Vol.E77-C   No.9   pp.1431-1436
Publication Date: 1994/09/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Heterostructure Devices and Epitaxial Growth Techniques)
nonalloyed ohmic contact,  n+-InGaAs,  MOVPE,  HEMT,  

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We fabricated and investigated HEMTs with nonalloyed ohmic contacts using highly conductive n+-ln0.5Ga0.5 As contact layers. We optimized the growth condition of n+-In0.5 Ga0.5As contact layers by MOVPE. Using WSi/W nonalloyed ohmic electrodes, we fabricated InGaP/InGaAs/GaAs pseudomorphic HEMTs with thermal stability of 500 for 30 minutes. In order to examine the scalability of HEMT devices, we tried to reduce the total size of HEMT devices to 3.2 µm using nonalloyed ohmic electrodes, which is the smallest value as far as we know. We could reduce the nonalloyed ohmic contact length Loh to 0.4 µm without degrading the device characteristics. Reducing the n+-In0.5Ga0.5As contact length LIGA to l µm however, decreased the transconductance gm by about 20%. We found that the scaling of the conventional nonalloyed HEMT structure is limited by LIGA.