Thermal stability of MISFET with low-temp molecular-beam epitaxy-grown GaAs and Al0.3Ga0.7As gate ins.

Citation
Rvvvj. Rao et al., Thermal stability of MISFET with low-temp molecular-beam epitaxy-grown GaAs and Al0.3Ga0.7As gate ins., IEEE RELIAB, 49(2), 2000, pp. 147-152
Citations number
21
Categorie Soggetti
Eletrical & Eletronics Engineeing
Journal title
IEEE TRANSACTIONS ON RELIABILITY
ISSN journal
00189529 → ACNP
Volume
49
Issue
2
Year of publication
2000
Pages
147 - 152
Database
ISI
SICI code
0018-9529(200006)49:2<147:TSOMWL>2.0.ZU;2-2
Abstract
GaAs and Al0.3Ga0.7As epilayers grown at LT (low-temperature) by MBE (molec ular beam epitaxy) were used as insulators in the fabrication of MISFET (me tal insulator semiconductor field-effect transistor) devices. Parametric ch anges were used to evaluate the thermal stability of MISFET, to identify fa ilure mechanisms and validate the reliability of these devices. A similar M ESFET was used as the reference in evaluating the MISFET performance. The L T-Al0.3Ga0.7As MISFET showed superior thermal stability. The degradation in the performance of MISFET with 1000 Angstrom thick LT-GaAs gate insulator was worse than those of the MESFET. On the other hand, MISFET with 250 Angs trom thick LT-GaAs gate insulators exhibited stable characteristics with th ermal stressing. LF (low frequency) noise studies on the TLM structures of MISFET layers exhibited 1/f noise in the LT-Al0.3Ga0.7As samples and 250 An gstrom LT-GaAs samples; whereas the 1000 Angstrom thick LT-GaAs samples exh ibited 1/f(3/2) noise, which was attributed to: i) the thermal noise genera ted at the interface of the insulator, and ii) the active layer due to the outdiffused metallic arsenic. Under thermal stress, this metallic arsenic c ontributed to composition changes at the interface in MISFET with thicker L T-GaAs gate insulators, To corroborate our claims, reverse gate-drain curre nt degradation experiments were carried out at 120 degreesC, 160 degreesC, 200 degreesC, and 240 degreesC. The activation energy obtained from these e xperiments for 1000 Angstrom thick LT-GaAs samples was 0.94 eV, which indic ated composition changes at the interface of insulator and active layer, Fo r further confirmation, transconductance frequency dispersion studies were carried out before and after thermal stress on these MISFET. The transcondu ctance of MISFET with 1000 Angstrom LT-GaAs gate insulators was degraded by 40% at 100 kHz after thermal stress. The rest of the samples exhibited sta ble characteristics. These results indicate that composition changes had occurred at the interfa ce in thicker LT-GaAs MISFET structures. Our studies showed that thinner LT -layers are ideal for achieving higher transconductance and better thermal stability without sacrificing the power capability of MISFET.