SURFACE-STATE DENSITY DISTRIBUTION OF SEMICONDUCTING DIAMOND FILMS MEASURED FROM THE AL CAF2/I-DIAMOND METAL-INSULATOR-SEMICONDUCTOR DIODESAND TRANSISTORS/
Y. Yun et al., SURFACE-STATE DENSITY DISTRIBUTION OF SEMICONDUCTING DIAMOND FILMS MEASURED FROM THE AL CAF2/I-DIAMOND METAL-INSULATOR-SEMICONDUCTOR DIODESAND TRANSISTORS/, Journal of applied physics, 82(7), 1997, pp. 3422-3429
Diamond metal-insulator-semiconductor diodes and field-effect transist
ors (MISFETs) have been prepared using CaF2 gate insulator and nondope
d (in some cases, boron was doped) diamond homoepitaxial films. The re
sultant capacitance-voltage (C-V) curves and drain current-drain volta
ge (I-D-V-D) curves strongly depended on the amount of oxygen contamin
ation of diamond surface. From analyses of C-V and I-D-V-D curves, it
was found that the oxygen contamination induced the surface states wit
h two distribution peaks locating very near the valence band edge and
at the energy of similar to 1 eV from the valence band edge. Although
fluorination of oxygen-terminated diamond surface proceeded to a certa
in extent during CaF2 deposition at the elevated temperatures in vacuu
m, it still allowed surface state formation of about similar to 10(14)
/cm(2) eV near the valence band edge due to uncompleted exchange of ox
ygen by fluorine atoms and easy penetration of residual oxygen in the
chamber through the CaF2 insulator at elevated temperatures. Reduced-o
xygen process by diamond surface passivation with hydrogen (hydrogenat
ion) and room temperature deposition of CaF2 greatly improved the surf
ace stability, and consequently, the surface state density near the va
lence band edge was reduced to similar to 10(12)/cm(2) eV. In this man
ner, the effective hole mobility of similar to 10 cm(2)/V s was obtain
ed from the diamond MISFET, which can be well compared with the surfac
e Hall mobility of 35 cm(2)/V s. (C) 1997 American Institute of Physic
s.