We demonstrate optical bistability in InP/InAlGaAs multi-quantum well(MQW) semiconductor ring lasers(SRL) which
are fabricated by the use of inductively coupled plasma reactive ion etching (ICP-RIE) and can be used in a multi-ring to
achieve all-optical storage. Unlike other international reports, the observed optical bistability has unidirectional regime
started directly from the threshold, skip the first two regimes and greatly reduce the injection current required in
applications. The device described in this article achieves threshold current 56mA which is quite low compared to other
reported devices, and some analysis and experiments on the etching depth have been done.
Silicon-based optical interconnection can solve the problem in interconnection of ULSI, can be used in optical
communication and can be used in optical calculation in future.
A complete Silicon base interconnection optoelectronic system is achieved, which is composed of light emitting
diode (LED), driver, detector, and amplifier. Main attention is to prove the feasibility to fulfill optical
transmission and detection in using Silicon material, and obtains enhancement of optoelectronic conversion
efficiency at the same time.
The phenomenon of electro-luminescence of Silicon positive intrinsic negative (pin) structure diode is
investigated. The optical spectral response of the system at 700nm indicates that the emitting light source has
low optical loss in Silicon. So the LED is suitable for Silicon optoelectronic interconnection system. The
detector is constructed with the same pin structure, the responsivity spectrum of the detector has a lot of
overlapping area with the spectrum of the LED. So, high transmission efficiency can be achieved in such a
system. Moreover, the driver and the amplifier circuit are all realized with Silicon material.
The performance of that system was tested in ordinary condition. The EL response time achieves to 100ns and
EL quantum efficiency achieves to 0.05%, which is a high level in Silicon optical interconnection.
This system is completely compatible with silicon on isolator (SOI) technique and can serve as a foundamental
basis of the research in the field of optical connection. Possible improvements for the optical connection system
have been discussed.
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.
In this paper, tunneling phenomena of tunneling junctions are studied and analyzed. Tunneling junction is the basic
structure of single electric transistor (SET) and other nano devices. Ultra fine oxidized titanium (Ti) lines are formed on
the Ti layer, which is 3nm thick and sputtered on a SiO2 substrate by magnetron sputtering. The atomic force microscope
(AFM)'s tip is used as a selective anodization electrode to oxidate the Ti film between electrode structures that are
formed by photo lithography. Ti-TiOx-Ti forms metal-insulator-metal (MIM) tunneling junction, and TiOx works as an
energy barrier for the electron. Different number of TiOx lines is fabricated between two electrodes by controlling
fabrication condition and environment at the same value. And then, the I-V characteristics of tunneling junctions with
different number of TiOx lines are measured. The results indicate that the tunneling phenomena of tunneling junctions
with different number of TiOx lines are different.
Titanium film with about 3nm thickness is deposited on SiO2-Si substrate with dual facing targets sputtering method. Nano-oxidation lines are fabricated on this Ti film with various biased voltages and for the first time, current monitoring is performed during the oxidation process using a contact-mode AFM. In the cases of all lines, a flow of current began immediately when the biased voltage was applied and it kept almost unchanged as each of the oxide line was growing. The level of detected currents during the fabrication of oxide lines on Ti film is in the microampere (μA) level. The detected currents increase linearly with the biased voltages, which indicates that the detected current is mainly tunneling current. Thus, the process of nano-oxidation of Ti film is controlled either by the tunneling of electrons or holes through the Ti/water interface.
Photo-generated carriers' transmission delay of a CMOS-Process-Compatible double photo-diode (DPD) is analyzed by using device simulation in this paper. The carriers' transmission delay of a DPD in CMOS N-well process consists of three parts: the delay in the P+ region, in the depletion region and in the N-well. The DPD equivalent circuit model, including photo-generated carriers' transmission delay, is given by means of device simulation. By comparing with different depth of the N-well and different area of the DPD, the delay of the diffusion part in the N-well and the delay of the junction capacitance are the most significant factors to determine the delay time of a DPD. In addition, the diffusion delay is relative to the depth, the doping concentration of the N-well and the bias. Adopting smaller size CMOS process is of benefit to improving the speed due to the shallow well, nevertheless the shallow well can cause the responsivity reduce. The responsivity reduce can be compensated by increasing the junction area.
In this paper, the photo-detected and controlled functions based on silicon photo-electronic Lambda transistor (PLBT) are reported. PLBT is composed of a npn vertical bipolar transistor as main device and a enhancement-mode MOSFET transistor as feedback device which connected in parallel across the base and collector terminals of bipolar transistor. Photo-electronic-lambda bipolar transistor (PLBT) is one important member of Si-photo electronic negative resistance devices. It has wide applications in photo-electronic coupler, light detector, light sensor and other photo-electronic circuit modules, which is significant for the further study of photo-electronic devices and circuits. When the Si-photo-electronic negative transistor device works as a load, it has two stable output states (bistability characteristics) with the change of the input light signals. Using the photo-bistable and self-locking characteristics of the PLBT, a photo-controlled Bistable Logic Circuit Element has been set up successfully. Through detail studying and analyzing to the operation feature and load feature of the photo-controlled bistable circuit, the nonlinear characteristic of the circuit is demonstrated. Furthermore the applications of this circuit element have been studied and verified.
With the development and application of nanofabrication on nano photoelectron device, the completely oxidized thin metal film such as titanium film by Atomic Force microscope (AFM) tip induced oxidation method has been used to make various nano electric devices. It is more and more important to study the process mechanism for improving the operational stability and reliability of such nano devices. In this paper, the mechanism of AFM tip induced oxidation is analyzed with several aspects. According to the experimental results of AFM tip induced oxidation of titanium under various voltage biases and scanning speeds, we find that the height of the titanium oxidation is linear with the voltage bias and with the negative log of the scanning speed. Based on the formers’ theories, the mechanism and the theoretical modeling of AFM tip induced oxidation are improved. By setting the proper conditions such as voltage bias of 8V and
scanning speed of 0.1μm/s, good nanofabrication results with AFM oxidation of titanium are got and the oxide lines are with good aspect ratio and good continuity.
The Resonant tunneling diode (RTD) is a high speed nanoelectronic device based on quantum resonant tunneling effect. It has the advantage of high frequency, low operating Voltage, low power dissipation, negative resistance, bistability and self-latching. It can be applied in high speed integrated circuits widely.
Based on the analysis of correlation between the device characteristic parameters and the material structure parameters, some design rules have been summarized as following:
1. The barrier width LB of RTD should be selected as narrow as possible to increase the peak current density Jp.
2. The well width LW should be selected slightly wider to decrease the peak Voltage Vp.
3. The spacer width LS should be selected slightly narrower to decrease the peak Voltage Vp.
4. The emitter doping density NE should be determined to a reasonable value to avoid both RS and intrinsic capacitance Cd too much.
5. Selecting AlAs as the barrier material to increase the barrier height then to increase peak valley current ratio (PVCR).
6. In emitter region, adding a narrow bandgap material layer to form a subwell. The 3dimension/2dimension resonant tunneling changes to 2dimension/3dimension resonant tunneling, the PVCR will be improved.
From above design rules, The GaAs based MBE material structure of RTD has been designed, The RTD devices have been fabricated from this material structure shown very good performance. Main characteristic parameters listed as following: Room temperature PVCR 7.6, fR=54GHZ, switching time tr≈171ps.
By using mixed-mode simulator in ATLAS, a commercial simulator produced by Silvaco International, a CMOS-process-compatible opto-electronic integrated circuit (OEIC) receiver is designed. The OEIC receiver can be used in optical communications or optical interconnections. The optical wavelength response, optical frequency response and optical pulse response of the OEIC receiver are simulated in 0.35 μm and 0.6 μm CMOS process. The sensitivity and the bandwidth of the OEIC receiver are optimized in giving detector area. Available receiver bandwidth is optimized under the given input optical power and detector area. The feedback voltage in trans-impedance amplifier is designed both for bandwidth and for sensitivity. The OEIC receiver was fabricated with a 0.6 μm CMOS process through MPW (multi-projector wafer) in China.
We first proposed monolithic optoelectronic integration of Resonant Tunneling Diode (RTD) and Heterojunction Bipolar Phototransistor (HPT). Circuit simulations using simple models of RTD and HPT successfully produced the optoelectronic bistable characteristics of RTD and HPT Negative Differential Resistance (NDR) device. The basic operation mechanism of Photoelectric Monostable-Bistable Transition Logic Elements (PMOBILE's) by utilizing the functionality of two series-connected RTDs in combination with HPT is also demonstrated by simulation.
By encapsulating a light emitting diode (LED) with a Silicon photo-negative resistance Device face to face in a hermetic package, a new type opto-isolator has been developed. Because of the features of Bistability and self-latching on the silicon photo-negative resistance devices, these non-linear opto-isolators present the response persistence function for the input signal. In this paper, the demonstration of response persistance function on PDUBAT type of silicon photo-negative resistance device has been made experimentally. The Dual Base Transistor (DUBAT) is a three terminals Voltage controlled negative resistance device, it is composed from the combination of a pnp type lateral bipolar transistor and a npn type vertical bipolar transistor. As DUBAT is radiated by light, the npn bipolar transistor is taken as a phototransistor. Thus the DUBAT will become a photo-DUBAT or PDUBAT. In PDUBAT, it is found that the photo-controlled "S" negative resistance characteristic can introduce a photo-controlled current switching effect and the persistance response functions, which keeps the response state for the input light signal until the reset signal changes the circuit from maintaining state to waiting state.