Guanghua Yang

CMOS-NDR transistor

In this paper, a novel device - MOS-NDR transistor is proposed and fabricated which is composed of four N-channel metal-oxide-semiconductor field effect-transistor (NMOS) devices. This MOS-NDR transistor could exhibit the negative differential resistance (NDR) characteristics similar to the conventional NDR device such as compound material based RTD (resonant tunneling diode) in the current-voltage characteristics by suitably modulating the MOS parameters, at the same time it could realize good modulation effect by the third terminal and has advantages of low working voltage (peak voltage Vp=0.7 V) and high PVCR (Peak to Valley Current Ratio) (nearly 10:1). The design and fabrication of this device are completely compatible with the standard 0.35 ¿m CMOS process, thus can considerably extend the functions of the CMOS circuits into new scope.

The Research of Operational Transconductance Amplifier

A topology structure of operational transconductance amplifier is proposed to be devised in this paper. In order to make it have the feature of high-speed, large bandwidth, and high stability, a two-stage cascode structure amplifier is designed by using cascaded single-stage amplifier. And several important parameters are calculated and analyzed theoretically. Finally the designed cascode two-stage amplifier is debugged by using Hspice. And the related parameter values are obtained. The magnification is more than 100dB, unity gain bandwidth is about 635MHz, and output swing is 4V. And the total transconductance of operational transconductance amplifier is 8.8A / V.

Study on temperature characteristic of green photodetector on Si substrate

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.

Light emission from Si LED controlling by a gate voltage and SOS tunneling junction

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 fabrication of high-brightness and high-power InGaAlP single-side red LED

In this paper, it is reported that the design and fabrication of high-brightness and high-power InGaAlP single-side red LED with electrodes which are interdigitated with the fingers. High-brightness and high-power InGaAlP LED is a new kind of visible light LED developed in recent years, which is driven by large current capacity, high luminous efficiency and excellent heat resistance. It has been used in various fields, such as large area displays, traffic lights, brake lights and so on. As compared with the conventional double-side LED, the single-side LED is more flexible to integrate with other devices and its fabrication is simplified. The size of chip is 1mm2. The fabrication of single-side LED, essentially, is the same as conventional LED, involving photolithography, PECVD SiO2, wet etching, evaporating, lift off and rapid thermal annealing using four masks. To control the widths of mesa and N electrode precisely, the selecting etch technique has been adopted, using HCL: H2O:H2O2 as the InGaAlP etching solution. I-V characteristics, light emission spectrum, luminous flux, luminous intensity and luminous efficiency of this LED have been measured. The characteristics are obtained with turn-on voltage of 1.5V and forward current of 400mA at its forward voltage of 3V. The peak wavelength is 635nm, which corresponds to red light, and the Full Width of Half Maximum is 16.4nm at injection current of 350mA. The luminous intensity is 830 mcd. The color coordinates is x=0.6943, y=0.3056 and the color index is 18.4. So we will conclude that the high-brightness and high-power InGaAlP single-side red LED will become new focus in both scientific research and industrial investment for its wide application.

The design and simulation of same Si-based device used as both LED and PD

A kind of new light emitting diode (LED) based on Si p-n junction forward injection mechanism completely compatible with standard Si-CMOS technology is designed and analyzed, which has higher efficiency than LED based on Si pn junction in reverse bias breakdown mode. At same time according to reversibility of optoelectronic conversion, the same Si-LED can be used as a photodetector (PD). The photoelectric characteristics of this device as both LED and PD are simulated by the commercial software SILVACO. This device is expected to have wide application in next generation optoelectronic integrated circuit (OEIC).