MQW Diode Research Articles

Single-chip imaging system that simultaneously transmits light

Multiple-quantum-well diodes (MQW diodes) naturally have key functionalities of light emission, transmission, modulation and detection all at the same time, enabling new forms of information and energy conversion between photons and electrons. When approximately biased and illuminated at the same time, a multifunctional MQW diode allows simultaneous light emission and detection within a single diode. A single-chip imaging system that uses a 4 × 4 MQW diode array is experimentally demonstrated here that can simultaneously transmit light and capture an image, showing the great development potential of advanced monolithic III-nitride information systems.

Structural dependence of optical bistability of In 0.52Al 0.48As/InP type II MQW diodes grown by gas source molecular beam epitaxy

The structural dependence of optical bistability was studied for the In 0.52Al 0.48As/InP type II multiple quantum well diodes grown by gas source molecular beam epitaxy. Two types of optical bistability were observed. One of them shows a sudden increase of light output with increasing injection current, while the other shows a sudden decrease of light output with increasing injection current. The former is considered to be induced by holes tunneling in the valence band, while the latter is considered to be induced by the resonant tunneling effect of electrons in the conduction band.

On the operational and manufacturing tolerances of GaAs-AlAs MQW modulators

We approach the question of optimization of surface-normal p-i(multiquantum-well, MQW)-n modulators from the viewpoint of investigating their tolerance to variations in wavelength and temperature and errors in manufacture. The reflection characteristics of two high-quality samples are carefully processed to eliminate Fabry-Perot fringes, and then their spectra at any bias are characterized with six phenomenological parameters which depend on /spl lambda//sub 0/, the zero-field exciton position. The two GaAs-AlAs samples have /spl lambda//sub 0/'s of 833.8 and 842.3 nm, and so cover a range useful for modulators designed to operate near 850 nm in the normally reflecting condition, i.e., reflection decreases with field. A linear interpolation of the parameters of these two samples is used to predict the behavior of MQW diodes with /spl lambda//sub 0/'s around this range, and so a fully comprehensive examination of normally reflecting MQW modulators is performed. The performance aspect that is examined is contrast ratio as a function of nonuniformities in the devices or operating conditions given a voltage swing of 3 V. There are two operational modes discussed. If the voltage offset of the bias is allowed to vary via a feedback circuit, a contrast of 2:1 may be maintained over an operating wavelength change (/spl Delta//spl lambda/) of 17 nm with local variations of wavelength of /spl plusmn/1 nm, which corresponds to a temperature variation of 60/spl deg/C while allowing for variations of laser driver wavelength of /spl plusmn/1 nm. If feedback Is not permitted, we determine that, given tolerances to manufacturing errors, a contrast of 1.5:1 may be maintained over a wavelength range of /spl sim/5 nm by either using stacked diode designs or extremely shallow quantum wells.

Bistability of electroluminescence in InAlAs/InP type II MQW diodes

Bistable behavior of electroluminescence (EL) was studied for the InAlAs/InP type II MQW diodes grown by gas source molecular beam epitaxy. The bistability of the current-light output ( I-L) characteristic is clearly observed at 80 K, and it exactly corresponds to the bistability of the current-voltage ( i–v) characteristic. The bistability shows a remarkable temperature dependence, and disappears above 200 K. It was found that subpeaks suddenly appear at the higher energy side of the main peak (1.28 eV) with increasing temperature. These subpeaks are attributed to the transition between the subband levels with different quantum numbers.

Temperature compensation of the threshold current,differential efficiency, andrefractive index of a GaInAs/InP MQW diode laser mounted on a bimetallicheatsink

The authors use stress from differential thermal expansion to provide temperature compensation of a 1.55 /spl mu/m MQW laser. Over the temperature range 20-70/spl deg/C, an equivalent characteristic temperature of 133 K, a reduced drop in the differential efficiency, and nearly complete elimination of the drift in modal wavelength are obtained.

Supply-function dependent sequential resonant tunneling in semiconductor multiple quantum well diodes

We have investigated the tunneling I–V characteristics of Al 0.3Ga 0.7As/GaAs MQW diodes with different electron densities, N s. Clear periodic negative differential resistances (NDRs) are observed for the samples with low N s, while NDRs are completely absent in the first plateau region of the I–V characteristics of the samples with high N s. It is found that such appearance/disappearance of periodic NDRs in the first plateau region of the I–V characteristics is controlled by the interplay of the transmission probability and the electron supply-function.

Blue and blue/green laser diodes and LED-based display devices

We describe the performance of pn junction MQW diode lasers and LEDs which are grown on both p-type and n-type GaAs substrates. Efforts to minimize dislocations by lattice matching the II–VI region to the GaAs substrate in some cases resulted in obtaining dislocation densities below 10 5 cm -2. We have obtained pulsed high power, high quantum efficiency laser emission up to room temperature conditions, and continuous operation at liquid nitrogen temperatures. Efficient LED and display devices operate in the blue (490–494 nm) at room temperature.

External grating tunable MQW laser with wide tuning range of 240 nm

A very wide tuning range in an external grating tunable InGaAs/InGaAsP MQW laser is demonstrated. Second subband recombination occurs in MQW diode at high current density injection. This contributes to gain expansion and a tuning range of 240 nm was obtained when operated continuously (CW) at room temperature.

High on/off ratio bistable operation of InGaAs/InAlAs MQW lasers using resonant tunneling effect

The structural dependence of the resonant tunneling characteristic in InGaAs/InAlAs MQW diodes is studied. It is found that the threshold current density for negative differential resistance caused by resonant tunneling effect increases with a decrease in the barrier width, well width and well number. In particular, the threshold current density increases by an order of one and a half when the barrier width decreases from 67 to 50 Å. Bistable operation with quite a high light output on/off ration (800:1) is obtained for the InGaAs/InAlAs MQW laser diodes with 50 Å width barriers using the resonant tunneling effect.