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Your search keyword '"Suihkonen, Sami"' showing total 11 results
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11 results on '"Suihkonen, Sami"'

3. Pushing the limits of non-radiative recombination suppression in GaAs/GaInP light-emitting diodes by doping profile engineering.

Author

Shahahmadi, Seyed Ahmad, Kivisaari, Pyry, Behaghel, Benoît, Radevici, Ivan, Suihkonen, Sami, and Oksanen, Jani

Subjects
AUDITING standards, CARRIER density, SPACE charge, GALLIUM arsenide, ELECTRIC fields, LIGHT emitting diodes, OPTOELECTRONIC devices, ENGINEERING
Abstract

Optimizing the efficiency of optoelectronic devices is challenging at low currents, even with high-quality materials, due to the dominance of non-radiative Shockley–Read–Hall recombination at low carrier densities. In this study, we nearly eliminate the typical non-radiative recombination current in a GaAs/GaInP double-heterojunction light-emitting diode (LED) by shifting the pn-junction 200 nm into the GaInP barrier layer on the n-side. This involves reducing the doping in the n-barrier to below the background p-type doping level to relocate the built-in electric field. As a result, the space charge recombination current with the ideality factor of two is strongly suppressed and remains concealed in our experimental dark current density–voltage measurements. The experimental results, coupled with our physics-based model, indicate the potential for considerable efficiency gains at current densities below ∼ 1 A/cm2. The findings prompt to carefully optimize the doping profiles of high efficiency LEDs and to reconsider the validity of using dark saturation currents as a metric for their performance. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Enhanced Specific Detectivity and UV-to-Visible Rejection-Ratio of Visible-Blind Metal– Semiconductor–Metal Photodetectors, Based on Epitaxial GaN/Si(111)

Author

Pal, Pinki, Kaur, Amadeep, Suihkonen, Sami, Lemettinen, Jori, Laha, A., Dhar, Subhabrata, Mahapatra, Suddhasatta, Indian Institute of Technology Bombay, Department of Electronics and Nanoengineering, Aalto-yliopisto, and Aalto University

Subjects
responsivity, epitaxy, thermionic field emission, specific detectivity, direct tunneling, Gallium Nitride (GaN), visible-blind photodetectors (PDs), UV-to-visible rejection-ratio (UVRR), Poole–Frenkel (PF) effect, thermionic emission (TE)
Abstract

A very high specific detectivity and UV-to-visible rejection-ratio (UVRR) is reported for visible-blind metal–semiconductor–metal (MSM) photodetectors (PDs), fabricated with gallium nitride (GaN) on Si(111) epitaxial layers. Comprehensive analysis of different figures-of-merit (FOM) reveals that the high specific detectivity results from a large responsivity in the UV-A region of the electromagnetic spectrum, and extremely low dark current, of the PDs. The current transport mechanisms in the absence and presence of illumination suggest that an internal gain, which is attributable to photo-induced barrier lowering, is responsible for the large responsivity of the PDs. The dark current is reduced due to the use of platinum-gold (Pt/Au) Schottky contacts, characterized by a relatively high Schottky barrier height. The vast improvement of nearly all FOMs, compared to those reported earlier for GaN/Si PDs, is highly encouraging for the development of low-cost, large-area arrays of visible-blind PDs.

Published
2023

10. Impurity diffusion in ion implanted AlN layers on sapphire substrates by thermal annealing

Author

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Okumura, Hironori, Watanabe, Yasuhiro, Shibata, Tomohiko, Yoshizawa, Kohei, Uedono, Akira, Tokunaga, Hiroki, Koseki, Shuuichi, Arimura, Tadanobu, Suihkonen, Sami, Palacios, Tomás, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Okumura, Hironori, Watanabe, Yasuhiro, Shibata, Tomohiko, Yoshizawa, Kohei, Uedono, Akira, Tokunaga, Hiroki, Koseki, Shuuichi, Arimura, Tadanobu, Suihkonen, Sami, and Palacios, Tomás

Abstract

Abstract We report on impurity diffusion in ion implanted AlN layers after thermal annealing. Silicon, tin, germanium, and magnesium ions were implanted into single-crystal Al-polar AlN layers grown on sapphire substrates. By annealing at 1600 °C, silicon and magnesium atoms were diffused in the AlN layer, while less change was observed in the distribution of germanium atoms. Silicon implantation introduced vacancy-related defects. By annealing at temperatures over 1300 °C, the vacancy-related defects were reduced, while oxygen atoms were diffused from the substrate due to sapphire decomposition. We reproducibly achieved silicon-implanted AlN layers with electrical conductance by controlling the annealing temperature and distribution of silicon and oxygen concentrations.

Published
2022

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