Resonant Cavity Enhanced Photodetectors Research Articles

RCE photodetectors based on VCSEL structures

We have fabricated top illuminated resonant cavity enhanced (RCE) detectors by partially removing top-mirror pairs of a vertical-cavity surface-emitting laser (VCSEL) structure by etching. The observed maximum quantum efficiency is 73% with a spectral full-width at half-maximum (FWHM) of about 1.7 nm. This particular RCE detector was fabricated by etching away 8 top-mirror pairs of a VCSEL structure, with 15.5 top-mirror pairs remaining. Spectral FWHMs as wide as 6.5 nm, with a peak efficiency of 36%, have been measured in the case of 4.5 top mirrors remaining. An increase in the 3-dB detector bandwidth up to 2.8 GHz is observed by reducing the active device diameter from 90 to 20 μm.

Growth of resonant-cavity enhanced photodetectors by MBE with in situ feedback control using spectroscopic ellipsometry

Precise control of layer thickness and alloy compositions are very critical for the successful growth of vertical cavity surface emitting lasers (VCSEL) and resonant cavity enhanced photodetectors (RCEPD). In traditional MBE, the growth of these devices requires extensive calibrations. Recently, spectroscopic ellipsometry (SE) was shown to be an accurate method for determining the composition and thicknesses of III–V semiconductor layers in situ during growth. This paper reports the growth of AlAs/GaAs/InGaAs RCEPDs using SE control with no a priori calibration curves. The experimentally measured cavity resonance of the reflectivity spectrum and the photoresponse peak of the fabricated photodiode lie within 3 nm of the target design value of 990 nm. These results show that feedback control during MBE allows quicker and more reproducible growth of RCEPDs with precise control of layer thickness and alloy composition than calibration-based control.

Characteristic analysis of resonant-cavity-enhanced (RCE) photodetectors

Analyses of light field distribution within a lossy resonant-cavity-enhanced (RCE) p-i-n photodetector is performed. A new expression for the field distribution inside the cavity is derived. This expression is used to derive an expression for the quantum efficiency taking into account the standing wave effect. The field distribution expression is also used in the continuity equations to derive and evaluate the frequency response of the RCE photodetector.

Electrically tunable GaAs/AlGaAs MQW RCE photodetector

The growth and characterisation of electrically tunable resonant cavity enhanced (RCE) photodiodes are described. Tuning is accomplished utilising the quantum confined Stark effect in GaAs/AlGaAs multiquantum wells. This structure is integrated into an asymmetric Fabry-Perot optical resonator formed by an AlGaAs/GaAs Bragg reflector and the semiconductor-air interface.

Polarization sensing with resonant cavity enhanced photodetectors

We describe a new method of sensing the linear polarization of light using resonant cavity enhanced (RCE) photodetectors. The RCE detectors are constructed by integrating a thin absorption region into an asymmetric Fabry-Perot cavity. The top reflector is formed by the semiconductor air interface while the bottom mirror is a distributed Bragg reflector (DBR). Quantum efficiency of these RCE devices can be controlled by tuning the cavity length by recessing the top surface of the detector for off-normal incidence of light the reflectivity of the semiconductor-air interface can be significantly different for TE(s) and TM(p) polarizations. A pair of monolithically integrated RCE photodetectors with cavity lengths tuned for resonance and antiresonance provide a large contrast in response to TE and TM polarizations. An alternative polarization sensor can be formed by vertically integrating a conventional and a RCE photodetector. We show that a large contrast in the TE/TM responsivities of the vertical cavity polarization detectors (VCPD) can be achieved, thus combining detection and polarization sensing in a single mesa semiconductor device. These devices alleviate the problems associated with the bulkiness and critical alignment constraints of the conventional sensors based on polarizing filters or splitters and have potential for fabrication of monolithic smart pixels and imaging arrays.

Polarisation sensing with resonant cavity enhanced photodetectors

The authors describe a new method of polarisation sensing using resonant cavity enhanced (RCE) photodetectors. The RCE detectors are constructed by integrating a thin absorption region into an asymmetric Fabry-Perot cavity formed by a bottom mirror composed of a distributed Bragg Reflector and the semiconductor air interface. Quantum efficiency of these RCE devices can be controlled by tuning the cavity length by recessing the top surface of the detector. For off-normal incidence of light, the reflectivity of the semiconductor-air interface can be significantly different for TE (s) and TM (p) polarisations. A pair of monolithically integrated RCE photodetectors with cavity lengths tuned for resonance and anti-resonance provide a large contrast in response to TE and TM polarisations. The device formed by this technique eliminates the need for external polarisation filters and beam splitters, thus alleviating the problems associated with the bulkiness of the polarisation sensors in many applications.

Resonant cavity enhanced photonic devices

We review the family of optoelectronic devices whose performance is enhanced by placing the active device structure inside a Fabry-Perot resonant microcavity. Such resonant cavity enhanced (RCE) devices benefit from the wavelength selectivity and the large increase of the resonant optical field introduced by the cavity. The increased optical field allows RCE photodetector structures to be thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. Off-resonance wavelengths are rejected by the cavity making RCE photodetectors promising for low crosstalk wavelength division multiplexing (WDM) applications. RCE optical modulators require fewer quantum wells so are capable of reduced voltage operation. The spontaneous emission spectrum of RCE light emitting diodes (LED) is drastically altered, improving the spectral purity and directivity. RCE devices are also highly suitable for integrated detectors and emitters with applications as in optical logic and in communication networks. This review attempts an encyclopedic overview of RCE photonic devices and systems. Considerable attention is devoted to the theoretical formulation and calculation of important RCE device parameters. Materials criteria are outlined and the suitability of common heteroepitaxial systems for RCE devices is examined. Arguments for the improved bandwidth in RCE detectors are presented intuitively, and results from advanced numerical simulations confirming the simple model are provided. An overview of experimental results on discrete RCE photodiodes, phototransistors, modulators, and LEDs is given. Work aimed at integrated RCE devices, optical logic and WDM systems is also covered. We conclude by speculating what remains to be accomplished to implement a practical RCE WDM system.

Resonant cavity-enhanced (RCE) photodetectors

The photosensitivity characteristics of resonant cavity-enhanced (RCE) photodetectors are investigated. The photodetectors were formed by integrating the active absorption region into a resonant cavity composed of top and bottom (buried) mirrors. A general expression for quantum efficiency for RCE photodetectors was derived taking the external losses into account. Drastic enhancement in quantum efficiency is demonstrated at resonant wavelengths for a high quality factor Q cavity with a very thin absorption layer. An improvement by a factor of four in the bandwidth-efficiency product for RCE p-i-n detectors is predicted. Molecular beam epitaxy grown RCE-heterojunction phototransistors (RCE-HPT) were fabricated and measured demonstrating good agreement between experiment and theory. >