Dmitrii G. Esaev

Design and optimization of GaAs∕AlGaAs heterojunction infrared detectors

Design, modeling, and optimization principles for GaAs∕AlGaAs heterojunction interfacial workfunction internal photoemission (HEIWIP) infrared detectors for a broad spectral region are presented. Both n-type and p-type detectors with a single emitter or multiemitters, grown on doped and undoped substrates are considered. It is shown that the absorption, and therefore responsivity, can be increased by optimizing the device design. Both the position and the strength of the responsivity peaks can be tailored by varying device parameters such as doping and the thickness. By utilizing a resonant cavity architecture, the effect of a buffer layer on the response is discussed. Model results, which are in good agreement with the experimental results, predict an optimized design for a detector with a peak response of 9A∕W at 26μm with a zero response threshold wavelength λ0=100μm. For a λ0=15μm HEIWIP detector, background limited performance temperature (BLIP temperature), for 180° field of view (FOV) is expected a...

Resonant cavity enhancement in heterojunction GaAs/AlGaAs terahertz detectors

The room-temperature absorption and reflection spectra in the range of 5–100 μm (3–60 THz) for multilayer heterojunction interfacial work function internal photoemission (HEIWIP) GaAs/AlGaAs far-infrared (FIR) detectors are presented. Calculated results based on the free carrier absorption and interaction with optical phonons are found to be in good agreement with the experimental results. Experimental responsivity spectra demonstrate the expected maxima from the absorption measurements due to resonant cavity effects. It is shown that the resonance cavity architecture enhances the performance of the FIR HEIWIP detectors and further improvement is proposed through the use of n++ and p++ bottom contact layers or doped substrates.

Near- and far-infrared p‐GaAs dual-band detector

A dual-band homojunction interfacial workfunction internal photoemission infrared detector that responds in both near- and far-infrared (NIR and FIR) regions is reported. In the p+‐i‐p+ detector structure, the emitter is carbon doped to 1.5×1019cm−3, and a 1μm thick GaAs layer acts as the barrier, followed by another highly p-doped GaAs contact layer. The NIR response is due to the interband transition in GaAs barrier layer and the threshold wavelength observed at 0.82μm is in good agreement with the 1.51eV band gap of GaAs at 4.2K. The intraband transition giving rise to FIR response is observed up to 70μm. Interband responsivity was (under 100mV reverse bias at 20K) ∼8A∕W at 0.8μm, while the intraband responsivity was ∼7A∕W. The detector has peak detectivities D*∼6×109 and 5×109cmHz1∕2∕W at 0.8 and 57μm wavelengths, respectively, under 100mV reverse bias at 20K.

High performance single emitter homojunction interfacial work function far infrared detectors

Results are reported on p-GaAs homojunction interfacial work function internal photoemission far infrared (HIWIP FIR) detectors with a ∼1019 cm−3 carbon doped single emitter and a barrier layer for three different barrier thicknesses. A remarkably high quantum efficiency with low dark current and an increased responsivity were observed for devices with 1-, 0.1-, and 4-μm-thick barrier regions. The dark current densities for these structures are on the order of 1–10 μA/cm2 at 4.2 K, corresponding to a high dynamic resistance compared with previous HIWIP FIR detectors. A detector with a barrier thickness of 1 μm had a peak responsivity of 18.6 A/W, a peak detectivity D*=9×1011 cmHz/W, and a quantum efficiency of 40% at a wavelength of 58 μm under a reverse bias measured at 4.2 K. Cutoff wavelengths of these detectors vary with bias and are around 70 μm as expected. The main features of the absorption and responsivity spectra are well described based on a model incorporating free carrier absorption, hot hole...

20 μm cutoff heterojunction interfacial work function internal photoemission detectors

Results are reported on Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors designed for operation up to 20 μm. The peak response of 100 mA/W at 12.5 μm with a D* of 2×1011 Jones was observed with a cutoff wavelength of ∼20 μm. The BLIP temperature for the devices was 40 K at 1.5 V bias. While the peak response remained almost constant (∼95 mA/W) up to 40 K, the D* reduced to 5×109 Jones due to the increased dark current. The response increased with doping while the dark current did not change significantly. Hence, higher responsivity and D* can be expected for designs with higher doping. Designs utilizing increased reflection from the bottom contact are suggested to improve the resonant cavity enhancement for optimizing the detectors, which should lead to higher D* and BLIP temperature.

Free carrier absorption in Be-doped epitaxial AlGaAs thin films

Free hole absorption in doped AlxGa1−xAs films, grown by molecular-beam epitaxy on semi-insulating GaAs substrates, was investigated. Free carrier absorption for three different hole concentrations with the same Al fraction and for two different Al fractions with the same doping concentration was studied. Experimental absorption coefficients were obtained from the data using a model that includes multiple reflections in the substrate wafer. In the 100–400μm range, (3,5,8)×1018cm−3 Be-doped Al0.01Ga0.99As films have absorption coefficients of ∼(3,3.5,5)×103cm−1, respectively, where the magnitude of the absorption is found to be almost independent of the wavelength. This allows replacing doped GaAs emitters in heterojunction interfacial work function internal photoemission far-infrared (HEIWIP) detectors with p‐AlxGa1−xAs layers with x<0.017 facilitating the extension of the threshold wavelength of HEIWIP detectors beyond the 92μm limit due to the practical Al fraction growth limit of 0.005 in molecular-bea...

Resonant cavity enhanced GaAs/AlGaAs IR detectors

HEterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors have been demonstrated with cutoff wavelengths λc up to 92 μm. One method of increasing the response in a desired range is to employ the cavity effect to create resonant maxima. Results are reported here confirming the presence of cavity enhancements in both the absorption and the detector response of HEIWIP structures at the 3λ/4 resonance. The detectors consisted of 13, 19 and 30 Be doped GaAs emitter and undoped Al0.02Ga0.98As barrier layers. Transmission and reflection spectra for multilayer GaAs/AlGaAs IR detectors in the range 2000-100 cm-1 at room temperature are presented. Comparisons with the calculated results based on free carrier absorption and interaction with optical phonons model are reported. It is shown that the absorption can be maximized by using the resonant cavity effect. The use of the resonant cavity effect should allow the design of detectors with increased response in the desired wavelength ranges.

Effect of doped substrate on GaAs-AlGaAs interfacial workfunction IR detector response through cavity effect

In this paper, results are reported showing response enhancement in GaAs-AlGaAs IR detectors using a doped substrate to increase reflection, enhancing the resonant cavity effect. Responsivity for heterojunction interfacial workfunction detectors grown on semi-insulating (SI) and doped substrates are compared. For a device grown on an SI substrate, a 9-/spl mu/m resonance peak had a response of 1.5 mA/W while a similar device on an n-doped substrate showed 12 mA/W. Also, the difference between response under forward and reverse bias (3 versus 12 mA/W) for the sample grown on the doped substrate, as well as calculated results confirm that the increased response is due to the resonant enhancement. An optimized design for a 15-/spl mu/m peak (24 /spl mu/m 0 response threshold) detector grown on a doped substrate could expect a peak response of 4 A/W with a 50% quantum efficiency and D/sup */ /spl sim/ 2 /spl times/ 10/sup 10/ Jones at the background limited temperature of 50 K.