S.K. Sargood

Integrated inversion channel optoelectronic devices and circuit elements for multifunctional array applications

An approach to laser-based optoelectronic integration is described. It is shown that by using a single epitaxial growth structure and a common processing sequence, all the electrical and optical devices required for a complete optoelectronic integrated circuit (OEIC) are realized. The demonstrated individual device performance and the implementation of an integrated combination of devices are discussed. Such applications as the implementation of a basic building block for a 2*2 smart-pixel switching node are discussed. A comparison to other laser- and modulator-based approaches is presented. >

Demonstration of the heterostructure field‐effect transistor as an optical modulator

A new semiconductor waveguide absorption modulator is demonstrated utilizing the heterostructure field‐effect transistor structure. The modulator of 300 μm length and 10 μm width achieves an extinction ratio of 8 for a gate voltage change of 2.5 V and an absorption change greater than 2300 cm−1. The transistor transconductance is 92 ms/mm for a 1 μm device and an identical structure has been reported as an edge‐emitting laser providing an ideal combination for optoeletronic integration.

A quantum-well inversion channel heterostructure as a multifunctional component for optoelectronic integrated circuits

An approach to optoelectronic integration utilizing a universal heterostructure with a single GaAs quantum-well active region is presented. The inversion channel forms the basis of a heterojunction field-effect transistor, a lateral current injection laser, a field-effect modulator, and a waveguide photodetector by simple reconfiguration of the electrodes and device geometry. The fabrication technology has been developed for gigahertz bandwidth applications by utilizing ion implantation techniques for interdevice electrical isolation and surface planarization, and reactive ion-etching to realize a self-aligned transistor-based heterostructure. The design, fabrication, and characterization of various heterostructures are discussed in the context of optoelectronic integration and the implementation of ion implantation disordering to realize low-loss self-aligned waveguides for on chip signal routing. The ultimate performance of the devices using a GaAs quantum well is considered, as well as the development of this technology for improved performance using strained InGaAs wells. >

A high-efficiency vertical-cavity surface-emitting switching laser fabricated with post-growth cavity mode positioning

The first room-temperature continuous-wave (CW) operation of the double heterostructure optoelectronic switching laser implemented as a vertical-cavity laser is described. A deposited dielectric top reflector of SiO/sub 2//TiO/sub 2/ allowed the use of a cavity etch back technique after the sample was grown, to position the cavity mode at the desired wavelength. Room temperature CW threshold currents as low as 4.8 mA for a 14- mu m-diameter device were obtained with slope efficiencies of 0.45 mW/mA. The maximum CW output power was 2.5 mW and the resistivity was 4*10/sup -4/ Omega cm/sup 2/.<<ETX>>

Operation of a single quantum well heterojunction field‐effect photodetector

The single quantum well heterojunction field‐effect photodetector is demonstrated for the first time as a GHz bandwidth waveguide heterostructure, and as the optoelectronic counterpart to the single quantum well heterojunction field‐effect transistor. For a 1 μm gate‐length device a responsivity of 0.16 A/W, external quantum efficiency of 0.35, and test‐laser limited rise time of 100 ps are obtained.

An Inversion Channel Technology For Opto-Electronic Integration

A new approach to optoelectronic integration is reported which combines electronic and optical devices fabricated with a common sequence and a single MBE wafer growth. The devices have in common, an inversion layer structure produced by charge sheet doping.

The inversion channel resonant-cavity enhanced photodetector for two-dimensional optoelectronic array applications

The operation of the inversion-channel resonant-cavity enhanced (RCE) photodetector in a configuration compatible with the vertical-cavity surface-emitting laser (VCSEL) is discussed. The phototransistor uses three strained InGaAs/GaAs quantum wells as the absorbing region and a post-growth dielectric top stack. A quantum efficiency of 41% was obtained at the resonant wavelength of 0.94 mu m, thereby giving a resonant-enhancement factor of 13.5. A bipolar transistor gain of 6.8 at a current density of 10 A/cm/sup 2/ allowed the phototransistor responsivity to reach 2.1 A/W at the resonant wavelength.<<ETX>>

Lasing oscillations in the negative differential resistance region of the double-heterostructure optoelectronic switch

In the characterization of the double-heterostructure optoelectronic switch (DOES) in the negative differential resistance (NDR) region, current oscillations are observed. The oscillations arise from the natural resonance of the NDR in the test circuit and produce a corresponding optical output. The authors observe these oscillations in DOES lasers with broad area threshold densities of 78 A/cm/sup 2/ and threshold currents for 10 mu m stripes of 15 mA. The optical output during the oscillations is laser emission since the current easily exceeds the laser threshold. The average output power due to the oscillations exceeds the CW power corresponding to the DC current by more than an order of magnitude.<<ETX>>

Electronic/photonic inversion channel technology for optoelectronic ICs and photonic switching

A new approach to optoelectronic integration is presented in which all optical and electronic devices are derived from a single crystal growth and a single fabrication sequence. The approach uses a self-aligned inversion channel capable of functioning as an FET or bipolar transistor, a detector, a modulator or a laser in either an analog or a digital mode. Topics discussed include a three-terminal switching laser, a bipolar inversion channel field-effect transistor, a three-terminal analogue laser, an HFET detector, and an HFET optical modulator.

Inversion-channel resonant-cavity-enhanced field-effect photodetector for 2D OEIC applications

The operation of the inversion-channel Resonant-Cavity Enhanced (RCE) photodetector is demonstrated in a configuration compatible with the Vertical Cavity Surface Emitting Laser (VCSEL). The phototransistor used 3 strained InGaAs/GaAs quantum wells as the absorbing region and a post-growth dielectric top stack. A quantum efficiency of 41% was obtained at a resonant wavelength of 0.94 micrometers , thereby giving a resonant enhancement factor of 13.5. A bipolar transistor gain of 6.8 at a current density of 10 A/cm2 allowed the phototransistor responsivity to reach 2.1 A/W at the resonant wavelength. We also demonstrate the movement of the resonant peak through the use of Focussed Ion-Beam (FIB) etching which has potential applications in Wavelength Division Multiplexed (WDM) systems.