M. Whitehead

MOVPE grown MQW pin diodes for electro-optic modulators and photodiodes with enhanced electron ionisation coefficient

Abstract Atmospheric pressure MOVPE has been used to prepare AlGaAs/GaAs MQW pin diodes exhibiting well-resolved room temperature exciton resonances and large reverse field breakdowns. The MQW i regions have been optimised by applying growth conditions which minimised the residual carbon concentration associated with the reagent TMA. Diodes with MQWs of well width 40 to 160 A have been assessed for the quantum confined Stark effect (QCSE) by photocurrent spectra and as absorption modulators. A 75 period 50 A Al 0.3 Ga 0.7 As/60 A GaAs i region gave a transmission change of 20% at 828 nm for 16 V applied bias. Diodes have also characterised for hole and electron ionisation rates when biased as avalanche detectors. An electron-to-hole ionisation rate ratio enhancement of 14 was observed for a 45 period 58 A Al 0.3 Ga 0.7 As/105 A GaAs MQW.

Effects of well width on the characteristics of GaAs/AlGaAs multiple quantum well electroabsorption modulators

We compare the characteristics of three electroabsorption modulators fabricated using GaAs/AlGaAs multiple quantum well structures with well widths 47, 87, and 145 A. We find that the narrow well structure provides the largest change in transmission. The 87 A well structure provides the largest contrast ratio, while the wide well sample offers the lowest operating voltage.

THE DESIGN AND APPLICATION OF III-V MULTIQUANTUM WELL OPTICAL MODULATORS

The application of an electric field across a quantum well structure induces a shift in the exciton dominated absorption edge. This effect is exploited in a number of optoelectronic devices including electro-absorption modulators, electron-refraction modulators, and optoelectronic logic devices. We will discuss how such modulators may be designed to operate at low voltages, with large changes in transmission or reflection and at high speeds. The choice of well widths, barrier widths, the use of coupled wells, and the enhancement due to Fabry Perot structures will all be considered. Results will be included for GaAs-GaAlAs, GaInAs-InP, and GaAs on silicon structures. Applications of these devices in optical interconnection of electronic circuits, and optoelectronic logic will be reviewed.

GaAs multiple quantum well microresonator modulators grown on silicon substrates

We report new results on the modulation characteristics of GaAs/AlGaAs asymmetric Fabry-Perot modulators grown on silicon substrates. We discuss factors affecting device performance and evaluate these by growing p-i-n quantum well diodes, and multilayer reflector stacks on silicon. Using data from these test structures we have designed an asymmetric microresonator modulator and achieve, experimentally, a 40% reflection change with only 5 V and a contrast ratio of 7.4 dB, also with 5 V.

Three-terminal noninverting optoelectronic logic device.

A novel noninverting optoelectronic logic device using a GaAs/AlGaAs multiple-quantum-well modulator is demonstrated that combines electronic nonlinearity with optical input and output and is bistable. The device is bistable but displays hard limiting and an optical gain of 12.

Effect of device length and background doping on the relative magnitudes of phase and amplitude modulation in GaAs/AIGaAs PIN multiple quantum well waveguide optical modulators: erratum

This erratum Letter points out an error in the caption of Fig. 4 of this paper.

Hard Limiting Opto-electronic Logic Devices

We report the demonstration of two novel opto-electronic devices whose characteristics appear to make them suitable for optical logic. One of the devices may be developed into a NOR or NAND gate and the other into an OR or AND gate. The devices are based on the use of electronic gain together with optical input and output and the specific implementation uses a photo-transistor to provide photo-detection and gain and a GaAs/AlGaAs multiple-quantum-well (MQW) electro-absorption modulator [1] to enable optical output. The components are connected in such a way as to provide a characteristic suitable for logic [2]: the output is hard-limited, the input is isolated from the output and the switching time is potentially fast, Electronic nonlinearities are strong, giving the potential for low power switching, and are fundamentally fast and optical access has the potential of high data rate communication with low crosstalk.