High Performance GaAs MISFETs with Self-Assembled Nanodielectrics (26042)
Novel SAND organic dielectrics suitable for high-performance III-V semiconductor devices such as metal-insulator-semiconductor field effect transistors (MISFETs).
ADVANTAGE: New process for manipulating the complex GaAs surface chemistry and thin film organic dielectrics for III-V semiconductor devices. The SAND process is flexible, low-cost, and simpler to implement than previously reported dielectric deposition processes.
SUMMARY: Using III-V compound semiconductors as conduction channels to replace traditional Si or strained Si is an active research frontier due to the excellent electrical properties of these semiconductors. The principal obstacle to III‑V compound semiconductors rivaling the properties of Si electronics has been the lack of high-quality, thermodynamically stable insulators on GaAs (or on III‑V materials in general) that equal the outstanding properties of SiO2 on Si. In a completely different approach GaAs MISFETs with excellent performance have been fabricated using very thin self-assembled nanodielectrics (SANDs) as the insulating layer. SANDs are effective insulators in organic thin-film transistors (OTFTs) affording excellent leakage current density (~ 10-9 A/cm2, SiO2 on Si), capacitance (~0.025 pF/um2) and dielectric (k~16) properties. They are readily processed and amenable to standard microelectronic techniques.
GaAs MISFET devices (Fig.1) fabricated with 700-900 Å Si-doped (4×1017 /cm3) GaAs layer as the channel and a 1500 Å C-doped (5×1016 /cm3) GaAs buffer layer on a P+ GaAs substrate grown by MOCVD, GaAs surfaces were suitably pretreated prior to SAND deposition. Ti/Au structures were e-bean deposited, followed by lift-off gate electrode formation. A 1um length x 100um width gate MISFET with 5.5 nm and 16.5 nm thick type III SANDs exhibited very low gate leakage current densities (Fig. 2). The dielectric strength of this novel organic film is as high as 6 MV/cm, comparable to SiO2, Si3N4 or HfO2 inorganics. Figure 3 shows I-V characteristics for a 0.5-μm-gate-length GaAs MISFET with a 5.5 nm-thick SAND film. The 800 Å thick MOCVD GaAs channel layer leads to a maximum drain current of 280 mA/mm with a pinch-off voltage of -2.5 V. These results suggest new opportunities and dielectric materials for high-performance III-V semiconductor devices.
Tobin Marks, Antonio Facchetti, Gang Lu, Peide Ye, Han Chung Lin
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