In the paper, a silicon PN junction photodetector is developed on the basis of n-type single-crystal (100) silicon substrate.
The properties of this semiconductor photodetctor depend on the temperature to certain extent. We emphasize on the
study on temperature characteristic of the photodetector: Firstly, the temperature behavior of dark current at zero bias
voltage and wide temperature range was investigated. Results show that dark current increases exponentially with
temperature over room temperature. Secondly, the temperature behavior of photo current at zero bias voltage and wide
temperature range was studied. The temperature characteristic is analysesed in the theory and optimized.
A novel Si LED with three terminals has been designed and fabricated compatible completely with standard n-well
CMOS technology. It is composed by a combination of a forward biased p+-n junction controlling by gate voltage and a
poly-Si/ultrathin oxide/Si tunneling junction. The experimental results demonstrates that: (1)The optical emitting power
of LED increases with both forward p+-n junction current increasing and positive gate voltage increasing; (2) The optical
emitting power of LED still increases with gate Voltage increasing while p+-n junction forward current at zero; (3) The
spectra of the optical output power on wavelength λ occurs a peak near 1000nm. The results can be explained from the
enhancement on the p-n junction forward current by the gate voltage induced barrier lowering effect and the
S(poly-Si)OS tunneling junction theory.
The earlier astable multivibrator formed by silicon tunnel diode has the disadvantage of low speed and non-modulation.
NDRHBT is a novel type of HBT with NDR characteristics and high speed. Its NDR characteristics can be modulated by
the base voltage VBE or base current IB. So the astable multivibrator formed by NDRHBT has the advantage of high
speed, high frequency, bistability, and frequency modulation by VBE or IB. Thus, it can be applied widely in high
frequency oscillation circuits and high speed-digital circuits.
In this paper, it is demonstrated that the frequency of the astable multivibrator can be modulated by base voltage VBE.
The experimental result shows that the frequency of time interval between two adjacent pulses f1 varies from 7×104Hz
down to 2.5×104Hz as VBE changes from 4.5V to 6.5V and exhibits near a linear relationship. So it is can be used as an
efficient voltage controlled frequency modulator for pulse signal in high speed digital circuits.
Bipolar/MOSFET hybrid mode lateral transistor is a transistor in which both bipolar and MOSFET currents flow simultaneously. Because of (1) Good compatibility with CMOS technology; (2) Larger current driving capability and transconductance than MOSFET. So, it is suitable to be taken as a bipolar device in BiCMOS element. In this paper, the Si/SiGe heterostructure, under the gate, is introduced into the conventional bipolar/MOSFET hybrid mode transistor. So a hybrid mode transistor with a lateral n+-Si/p-SiGe/n+-Si structure parallel in base is formed, in which the heterostructure of E-B junction n+-Si/p-SiGe has a high injection electron current from E to B region and a low injection hole current from B to E region (result in by higher barrier for hole), then the total injection efficiency will increase. When this effect becomes a main mechanism than that of the barrier lowering in the surface depletion layer, the characteristics of the device will be dependent on the parameters of SiGe alloy, such as the mole number of Germanium etc. The device simulation of Si/SiGe heterojunction base hybrid mode transistor has been carried out by MEDICI program. The simulation results show that IC and hFE increase with Mole number of Ge increasing and WB decreasing, then the current gain and current capability are improved than that of conventional bipolar/MOSFET hybrid Mode transistor.
Lattice-matched InGaP on GaAs substrate was successfully grown by solid-source molecular beam epitaxy (SSMBE) with a GaP decomposition source. 0.5um-thick InGaP epilayer shows photoluminescence (PL) peak energy as large as 1.962eV, PL FWHM as small as 9.4meV, X-ray diffraction (XRD) rocking curve line-width as narrow as 25arcsec. The electron mobility of undoped, Si-doped InGaP layers measured by Hall are comparable to similar InGaP/GaAs heterojunction grown by SSMBE with other source or other growth techniques. Then the InGaP/GaAs HBT epiwafer is grown by this way. Beryllium(Be) diffusion is reduced by increasing the As/Ga flux ratio. Heterojuction Bipolar Transistor (HBT) with 75×75um2 emitter mesa area fabricated using this structure yielded an excellent performance with high current gain. The results reveal that InGaP/GaAs heterojunction grown by the present growth way have great potential application for semiconductor devices.