High-speed 1.55 μm operation of low-temperature-grown GaAs-based resonant-cavity-enhanced p–i–n photodiodes

Abstract

We report the design, growth, fabrication, and characterization of GaAs-based high-speed p–i–n photodiodes operating at 1.55 μm. A low-temperature-grown GaAs (LT-GaAs) layer was used as the absorption layer and the photoresponse was selectively enhanced at 1.55 μm using a resonant-cavity-detector structure. The bottom mirror of the resonant cavity was formed by a highly reflecting 15-pair GaAs/AlAs Bragg mirror. Molecular-beam epitaxy was used for wafer growth, where the active LT-GaAs layer was grown at a substrate temperature of 200 °C. The fabricated devices exhibited a resonance around 1548 nm. When compared to the efficiency of a conventional single-pass detector, an enhancement factor of 7.5 was achieved. Temporal pulse-response measurements were carried out at 1.55 μm. Fast pulse responses with 30 ps pulse-width and a corresponding 3 dB bandwidth of 11.2 GHz was measured.

High-performance visible-blind GaN-based p-i-n photodetectors

“…The samples were fabricated by a six-step microwavecompatible fabrication process [16][17][18] in class-100 clean room environment. The dry etching was accomplished by reactive ion etching ͑RIE͒ under CCl 2 F 2 plasma, 20 SCCM ͑SCCM denotes cubic centimeter per minute at STP͒ gas flow rate, and 200 W rf power conditions.…”

First-principles study of structural, electronic, and optical properties of surface defects in GaAs(001) - β2(2x4)

“…11 This allows photoabsorption as observed in many LT-GaAs experiments. 1,3,11 As clearly shown in the partial charge distribution in Fig. 9(c), the midgap state is related to the atoms near the vacancy, specifically, the As atom in the first layer which experiences dimer distortion due to the movement of the other As atom towards the Ga vacancy at the edge along the a direction.…”

“…The figure illustrates that absorption can occur below the bulk band gap (1.43 eV) which proves the ability of LTGaAs to detect low energy waves observed in several experiments due to the presence of defect. 1,3,37 The clean GaAs(001) -β2(2x4) structure also exhibits this finite absorption since the formation of As dimers on the surface with two As dimers missing created a non-stoichiometric GaAs surface as compared to the clean GaAs(001).…”

“…One of the remarkable properties of LT-GaAs, based on experiments, is the ability to absorb sub-bandgap wavelength photons (e.g., 1.56 µm). [1][2][3] The observed near linear but not completely linear excitation intensity dependence of photoconductivity suggests the two-step photon absorption mediated by midgap states, possibly formed by defects. 1 Very recently, this sub-bandgap-optical-excitation induced photoconductivity (SOEP) using a 1.56 µm probe was observed and confirmed the sequential charge carrier excitation via midgap states.…”

“…4 These midgap states are referred to in other literatures as defect states, deep energy level (EL) defects, deep traps, deep defects, and midgap defects. 3,[5][6][7][8] Defects in GaAs grown by molecular beam epitaxy (MBE) occur as a result of low-temperature growth in a range from 180 • C to 300 • C. This is lower than the normal epitaxial growth temperatures at around 580 • C to 600 • C. 9 Particle-induced x-ray (PIXE) analysis revealed that LT-GaAs consists of 1-1.25 at % excess As 10 which has been suggested as the source of the deep EL2-like defect (0.68 eV-0.92 eV). 8,[11][12][13] Several other deep-level defects were noted in experimental studies using electron paramagnetic resonance (EPR), thermally stimulated currents (TSC) spectra, deep level transient spectroscopy (DLTS) characterization, and deep center photoluminescence-excitation (PLE) spectra.…”