| Budget Amount *help |
¥14,400,000 (Direct Cost: ¥14,400,000)
Fiscal Year 2000: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1999: ¥10,900,000 (Direct Cost: ¥10,900,000)
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| Research Abstract |
(1) Results in 1999
(a) Al-depth profiles in n-type 6H-SiC doped with a pulsed excimer laser (KrF) processing method under the conditions of a constant pressure 100 Torr of the hydrogen-diluted TMA (trimethylaluminum) have been evaluated varying a number of laser pulses from 1000 to 8000 shots. They were approximated as sum of two complimentary error-functions ; the one nearer to surface ranging from 10 to 30 nm and the other inner one (tail distribution) from 20 to 100 nm. The investigations show that the aluminum depth profiles could be controlled between 20 and 100 nm according to the number of the laser pulses. A fraction of doped Al was electrically activated without any post heat treatments, and p-type conduction was confirmed with Hall effect and I-V measurements. Al-acceptor levels at E_v+0.239 eV was also confirmed with PL measurements.
(b) Ohmic contacts with W/Ti and Al/Ti to n- and p-type 6H-SiC substrates, respectively, have been refined with a pulsed laser processing using
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KrF excimer laser. The electrodes have very smooth surfaces and the contact resistivity of 6.7x10^<-5> and 1x10^<-3> Ωcm^2 for n- and p-type substrate, respectively. The contact interface regions are very thin comparing with the one produced with heat treatments at high temperature.
(2) Results in 2000
(a) Al-depth profiles in n-type 6H-SiC doped with a pulsed laser processing using a KrF excimer laser have reconfirmed the distribution of the both regions of 0 to 20 nm and 20 to 100 nm, which are approximated with the sum of the complimentary error-function. The surface Al concentrations estimated from the curve fitting are 9.0x10^<17>, 4.5x10^<18>, and 2.7x10^<19> Al/cm^3 for the respective gas pressure of TMA/H_2 10, 100, and 200 Torr, keeping constant an energy density of the laser pulse 1.2J/cm^2 and a number of laser shots 1000. The present investigations confirmed that Al-depth profiles could be controlled with three parameters such as the TMA/H_2 gas pressure and the laser energy density, and a number of laser shots.
(b) Thin pn junction diodes have been fabricated on the undoped n-type 6H-SiC (2.5x10^<115> N/cm^3) under the following conditions, TMA/H_2 ; 100 Torr, No.of shots ; 8000, and 1.2J/cm^2. Using a thin Al/Ti ohmic contact on the P-type doped-layer, the photo-responsivity has maximum external quantum efficiency 41% at the wavelength of 330 nm. Less
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