Characteristics and applications of nonlinear gain in low-dimensional
semiconductor lasers
Hidefumi AKIYAMA
Institute for Solid State Physics (ISSP), University of Tokyo
5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
E-mail: golgo@issp.u-tokyo.ac.jp
We fabricated well-controlled clean low-dimensional semiconductor lasers,
incorporating 1D quantum wires and 2D quantum wells with highly uniform interfaces and
layer structures showing sharp luminescence spectral widths into various device structures
such as p-n junctions, field-effect gate structures, optical waveguides, and optical cavities. For
these structures, we aim to measure various optical responses and many-body electron-hole
phases or states by controlling density of electrons and holes, temperature, and coupling
strength of photon and electrons, and to derive new optical effects and/or functions
originating from dynamically correlated clean electron-hole systems. Moreover, we study
nonlinear optical phenomena and effects in highly excited semiconductor lasers.
GaAs-based T-shaped quantum wires (T-wires) of 14 nm x 6 nm cross-sectional size
with interface high interface uniformity were fabricated by cleaved-edge overgrowth with the
molecular beam epitaxy on the interface improved by a growth-interrupt high-temperature
anneal [1], and were incorporated into lasers and field-effect-transistor-type (FET-type)
optical devices.
Ground state lasing was measured via optical pumping in single-quantum-wire lasers (T
< 60 K) and 20-quantum-wire lasers (T < 120 K) [2,3]. Via current injection, 15- and
20-quantum-wire lasers showed the lowest threshold of 0.27 mA at 30 K and the highest
temperature of 110 K [4-6]. Measurements of gain spectra via the Cassidy-Hakki-Paoli
method and simultaneous PL spectra demonstrated formation of gain due to biexcitons near
transparency densities and gain due to an electron-hole plasma at higher densities [7,8].
PL and PLE spectroscopy for a single-quantum-wire FET, or a modulation-doped single
quantum wire with a gate to tune 1D electron density, was achieved. With a non-degenerate
1D electron gas, the band-edge absorption exhibits a sharp peak structure induced by the 1D
density of states. When the dense 1D electron gas is degenerate at a low temperature, we
observe a Fermi-edge absorption onset with little many-body modification or Fermi-edge
singularity [9].
Comparison with theoretical calculations based on screened Hartree-Fock
approximations [10] and more advanced methods are in progress, which is revealing
interesting and important roles of Coulomb interactions, state filling, and one-dimensionality.
This study is based on collaborations with Prof. Yoshita in ISSP, University of Tokyo,
Dr. Loren Pfeiffer, Ken West in Bell Labs in U. S. A., Professors Tetsuo Ogawa, Kenichi
Asano in Osaka University, and Professor Ping Huai in Shanghai Institute of Applied Physics.
References:
[1] M. Yoshita, H. Akiyama, L.N. Pfeiffer, and K. W. West, "Formation of flat
monolayer-step-free (110) GaAs surfaces by growth interruption annealing during
cleaved-edge epitaxial overgrowth", Jpn. J. Appl. Phys. part2 40, L252 (2001).
[2] Y. Hayamizu, M. Yoshita, S. Watanabe, H. Akiyama, L. N. Pfeiffer, and K. W. West,
"Lasing from a single quantum wire", Appl. Phys. Lett. 81, 4937 (2002).
[3] H. Akiyama, L. N. Pfeiffer, M. Yoshita, A. Pinczuk, P. B. Littlewood, K. W. West, M. J.
Matthews, and J. Wynn, "Coulomb-correlated electron-hole plasma and gain in a
quantum-wire laser of high uniformity", Phys. Rev. B 67, 41302 (2003).
[4] Shu-man Liu, M. Yoshita, M. Okano, T. Ihara, H. Itoh, H. Akiyama, L. Pfeiffer, K. West,
and K. Baldwin, "Low-threshold Current-injection Single-mode Lasing in T-shaped
GaAs/AlGaAs Quantum Wires", Jpn. J. Appl. Phys. 46, L330 (2007).
[5] Shu-man Liu, M. Yoshita, M. Okano, T. Ihara, H. Itoh, H. Akiyama, L. N. Pfeiffer, K. W.
West, and K. W. Baldwin, "Electronic Structure and Efficient Carrier Injection in
Low-threshold T-shaped Quantum-wire Lasers with Parallel p- and n-doping Layers", J. Appl.
Phys. 102, 043108 (2007).
[6] M. Okano, Shu-man Liu, T. Ihara, H. Itoh, M. Yoshita, H. Akiyama, L. N. Pfeiffer, K.
West, and O. Malis, "Temperature-dependent current injection and lasing in T-shaped
quantum wire laser diodes with perpendicular p- and n-doping layers", Appl. Phys. Lett. 90,
091108 (2007).
[7] Y. Hayamizu, M. Yoshita, Y. Takahashi, H. Akiyama, C. Z. Ning, L. N. Pfeiffer, and K.
W. West, "Biexciton gain and the Mott transition in GaAs quantum wires", Phys. Rev. Lett.
99, 167403 (2007).
[8] M. Yoshita, Y. Hayamizu, H. Akiyama, L. N. Pfeiffer, K. W. West, "Exciton-plasma
crossover with electron-hole density in T-shaped quantum wires studied by the
photoluminescence spectrograph method", Phys. Rev. B 74, 165332 (2006).
[9] T. Ihara, Y. Hayamizu, M. Yoshita, H. Akiyama, L. N. Pfeiffer, and K. W. West,
"One-dimensional band-edge absorption in a doped quantum wire", Phys. Rev. Lett. 99,
126803 (2007).
[10] P. Huai, H. Akiyama, Y. Tomio, and T. Ogawa, "Coulomb Enhancement and
Suppression of Peak Gain in Quantum Wire Lasers", Jpn. J. Appl. Phys. 46, L1071 (2007); M.
Okano, P. Huai, M. Yoshita, S. Inada, H. Akiyama, K. Kamide, K. Asano, and T. Ogawa
"Robust carrier-induced suppression of peak gain inherent to quantum-wire lasers", J. Phys.
Soc. Jpn., 80, 114716 (2011).