Mid-wavelength infrared avalanche photodetector with AlAsSb/GaSb superlattice

In this work, a mid-wavelength infrared separate absorption and multiplication avalanche photodiode (SAM-APD) with 100% cut-off wavelength of ~ 5.0 µm at 200 K grown by molecular beam epitaxy was demonstrated. The InAsSb-based SAM-APD device was designed to have electron dominated avalanche mechanism via the band structure engineered multi-quantum well structure based on AlAsSb/GaSb H-structure superlattice and InAsSb material in the multiplication region. The device exhibits a maximum multiplication gain of 29 at 200 K under -14.7 bias voltage. The maximum multiplication gain value for the MWIR SAM-APD increases from 29 at 200 K to 121 at 150 K. The electron and hole impact ionization coefficients were derived and the large difference between their value was observed. The carrier ionization ratio for the MWIR SAM-APD device was calculated to be ~ 0.097 at 200 K.

Mid-wavelength Infrared Avalanche Photodetector with AlAsSb/GaSb Superlattice

This work demonstrates a mid-wavelength infrared separate absorption and multiplication avalanche photodiode (SAM-APD) with AlGaAsSb/GaSb multi-quantum well as the multiplication layer and InAsSb bulk material as the absorption layer. The InAsSb-based SAM-APD structure was grown by molecular beam epitaxy. The device exhibits a 100 % cut-off wavelength of ~5.3 µm at 150 K and ~5.6 µm at 200 K. At 150 K and 200 K, the responsivity of the SAM-APD reaches a peak value of 2.26 A/W and 3.84 A/W at 4.0 µm under -1.0 V applied bias, respectively. The SAM-APD device was designed to have electron dominated avalanching mechanism via the multi-quantum well structure as the avalanche architecture. A multiplication gain value of 29 at 200 K was achieved under −14.7 V bias voltage. The electron and hole impact ionization coefficients were calculated and compared. A carrier ionization ratio of ~0.097 was achieved at 200 K.

Radio spectral index distribution of SDSS-FIRST sources across optical diagnostic diagrams

Context. The empirical relations between supermassive black holes and their host spheroids point towards the crucial role of galactic nuclei in affecting the properties of their hosts. A detailed understanding of how the activity of a galactic nucleus regulates the growth of its host is still missing. Aims. To understand the activity and the types of accretion of supermassive black holes in different hosts, it is essential to study the radio-optical properties of a large sample of extragalactic sources. In particular, we aim to study the radio spectral index trends across the optical emission line diagnostic diagrams to search for potential (anti)correlations. Methods. To this goal, we combined flux densities from the radio FIRST survey at 1.4 GHz (with the flux density range 10 mJy ≤ F1.4 ≤ 100 mJy) for 396 SDSS sources at intermediate redshift (0.04 ≤ z ≤ 0.4) with the Effelsberg radiotelescope measurements at 4.85 GHz and 10.45 GHz. The information about the optical emission-line ratios is obtained from the SDSS-DR7 catalogue. Results. Using the Effelsberg data, we were able to infer the two-point radio spectral index distributions for star-forming galaxies, composite galaxies (with a combined contribution to the line emission from the star formation and AGN activity), Seyferts, and low ionization narrow emission region (LINER) galaxies. Conclusions. While studying the distribution of steep, flat, and inverted sources across optical diagnostic diagrams, we found three distinct classes of radio emitters for our sample: (i) sources with a steep radio index, high ionization ratio, and high radio loudness, (ii) sources with a flat radio index, lower ionization ratio, and intermediate radio loudness, (iii) sources with an inverted radio index, low ionization ratio, and low radio loudness. The classes (i), (ii), and (iii) cluster mainly along the transition from Seyfert to LINER sources in the optical diagnostic (Baldwin, Phillips & Telervich; BPT) diagram. We interpret these groups as a result of the recurrent nuclear-jet activity.

A Proposal to Apply Effective Acceptor Level for Representing Increased Ionization Ratio of Mg Acceptors in Extrinsically Photon-Recycled GaN

An effective acceptor level (EAeff) for representing the increased ionization ratio in extrinsically photon-recycled p-type GaN is proposed.EAeffat 300 K in the range of 0.1360.145 eV is found to reproduce current/voltage characteristics of transmission-line-model patterns formed with GaN p-n junction epitaxial layers and electrode spacing of 320 μm when the p-n diode current flowing through an 80×100-μm electrode is 90 mA. WhenEAeffis decreased from 0.160 eV to 0.145 eV, the on-resistance of 18×100-μm GaN bipolar transistors is predicted to be reduced by more than 50%.

Growth of Heavily Indium Doped Si Crystals by Co-Doping of Neutral Impurity Carbon or Germanium

Czochralski Growth of Si Crystals Heavily Doped with in Impurity and Co-Doped with Electrically Neutral Impurity C or Ge Was Conducted in Order to Investigate the Solubility and Ionization Ratio of in in Si for Utilizing in Advanced ULSI and PV Devices. The Carrier Concentrations in the Grown in-Doped and (In+C) and (In+Ge) Co-Doped Crystals Were in a Range of 3.5~6.5 × 1016 Cm-3, much Lower than the Total Concentration of in Impurity due to the Low Ionization Ratio. Sufficient Increase of Carrier Concentrations by Co-Doping of C or Ge Impurity Was Not Detected for their Low Concentrations in the Grown Crystals Investigated.