Quantum efficiency enhancement of AlGaAs/GaAs quantum well infrared detectors using a waveguide with a grating coupler

Abstract

Long wavelength quantum well detectors with very high quantum efficiency, based on the coupling of radiation into an optical resonant cavity or waveguide defined by a reflection grating coupler on one side of the infrared absorbing multiquantum well stack, and an aluminum arsenide cladding layer on the other, have been fabricated and the results compared with theory. Theory shows that quantum efficiencies up to 90% may be obtained (for polarized radiation). However, experimental results indicate that the response peak becomes broadened due to spread in the grating period and therefore the maximum quantum efficiency is in practice limited to 60%, corresponding to a current responsivity of 2.1 A/W. This is 2.7 times larger than for a 45° polished edge detector with the same quantum well characteristics.

Simulation and analysis of grating-integrated quantum dot infrared detectors for spectral response control and performance enhancement

“…However, for larger periods, we have stronger diffraction, and thus, we have large absorption in both x and z directions. Also note that this behavior is completely different from QW detectors 26,27 which allow light absorption in the z-direction (A z ) only. In our case, all A x , A y , and A z components contribute to the detector responsivity.…”

“…In fact, this also highlights the uniqueness of QD detectors compared to QW detectors. Grating structures have been used to enable optical coupling into QW IR detectors, 26,27 because they have light absorption only in one direction (along the growth direction). However, here we use subwavelength gratings patterned on a semiconductor contact to adjust resonance and light absorption conditions in the active QD layer.…”

640×486 long-wavelength two-color GaAs/AlGaAs quantum well infrared photodetector (QWIP) focal plane array camera

“…After the 2-D grating array (calculations of the 2-D grating parameters and light coupling experiments were discussed extensively in [14]) was defined by photolithography and dry etching, the LWIR detector pixels of the 640 x 486 FPA's were fabricated by dry etching through the photosensitive GaAs/Al x Gai_ x As MQW layers into the 0.5 /zm thick doped GaAs intermediate contact layer. All VLWIR pixels in the even rows of FPA's were short circuited.…”

“…Thus, the total thickness of 8-9 ßm detector is limited by the grating layer thickness of the VLWIR detector. This 2-D periodic grating structure is fabricated on the detectors by using standard photolithography and SF 6 :BC1 3 selective dry etching.After the 2-D grating array (calculations of the 2-D grating parameters and light coupling experiments were discussed extensively in [14]) was defined by photolithography and dry etching, the LWIR detector pixels of the 640 x 486 FPA's were fabricated by dry etching through the photosensitive GaAs/Al x Gai_ x As MQW layers into the 0.5 /zm thick doped GaAs intermediate contact layer. All VLWIR pixels in the even rows of FPA's were short circuited.…”

Antenna Structures for Optical Coupling in Quantum-Well Infrared Detectors

“…Previous QWIPs have used a variety of metalized diffraction gratings, including periodic [1][2][3][4][5] and pseudorandom [6] etched gratings, as well as periodic planar gratings [7]. These structures are generally designed to couple via propagating modes above the grating.…”