Emission spectra of InGaN/AlGaN/GaN quantum well heterostructures: Model of the two-dimensional joint density of states

Journal of Applied Physics

Minina

Tomm

et al. 2012

Efficient, narrow linewidth excitonic emission at room temperature from GaAs/AlGaAs V-groove quantum wire light-emitting diodesThe effects of uniaxial compression in [110] direction on energy-band structures, heavy and light hole mixing, optical matrix elements, and gain in laser diodes with "light hole up" configuration of valence band levels in GaAsP quantum wells with different widths and phosphorus contents are numerically calculated. The development of light and heavy hole mixing caused by symmetry lowering and converging behavior of light and heavy hole levels in such quantum wells under uniaxial compression is displayed. The light or heavy hole nature of each level is established for all considered values of uniaxial stress. The results of optical gain calculations for TM and TE polarization modes show that uniaxial compression leads to a significant increase of the TE mode and a minor decrease of the TM mode. Electroluminescence experiments were performed under uniaxial compression up to 5 kbar at 77 K on a model laser diode structure (pÀAl x Ga 1Àx As= GaAs 1Ày P y =nÀAl x Ga 1Àx As) with y ¼ 0.16 and a quantum well width of 14 nm. They reveal a maximum blue shift of 27 meV of the electroluminescence spectra that is well described by the calculated change of the optical gap and the increase of the intensity being referred to a TE mode enhancement. Numerical calculations and electroluminescence data indicate that uniaxial compression may be used for a moderate wavelength and TM/TE intensity ratio tuning. V C 2012 American Institute of Physics. [http://dx.

Section: Experimental Details and Sample Characterizationmentioning

confidence: 99%

Effect of uniaxial stress on electroluminescence, valence band modification, optical gain, and polarization modes in tensile strained p-AlGaAs/GaAsP/n-AlGaAs laser diode structures: Numerical calculations and experimental results

Journal of Applied Physics

Minina

Tomm

et al. 2012

“…The obtained EL spectra were analyzed in the frame of a model for the two-dimensional density of states in the active region successfully used earlier for light emitting diodes based on InGaN/AlGaN/GaN heterostructures [3]. The model takes into account potential fluctuations that change a step-like two-dimensional-joint density of states, describing interband transitions, to the inverse Fermi-like function with an exponential decay on the low energy side [7].…”

Section: Resultsmentioning

confidence: 99%

“…The EL spectra at currents, I , ranging from 0.1 to 30 mA were recorded using an automated system based on a MDR-12 monochromator with a spectral resolution better than 1 Å [3]. The spectra were averaged over 3/15 events of measuring at each particular point.…”

Section: Samples and Experimental Setupmentioning

confidence: 99%

Uniaxial compression influence on electroluminescence spectra inp-Al_xGa_1−xAs/GaAs_1−yP_y/n-Al_xGa_1−xAs heterostructures

Minina

Kissel

et al. 2008

High Pressure Research

We present new results on the influence of uniaxial stress up to P = 400 MPa along [110] direction on the electroluminescence (EL) spectra of p-Al x Ga 1−x As/GaAs 1−y P y /n-Al x Ga 1−x As double heterostructures. With increasing stress, the emission spectra demonstrate a blue shift of up to 20 meV at a pressure of P = 400 MPa, while the EL intensity increases under compression. The results are discussed in terms of changes in the band structure under uniaxial compression.

“…The automated system for the recording of EL spectra was based on a MDR-12 monochromator and provides precise measurements with a spectral resolution better than 1 Å (0.3-0.4 meV) [8]. The measurements were carried out with a step width of 1 nm and averaged over 3−15 events of measuring at each particular point.…”

Section: Samples and Experimental Setupmentioning

confidence: 99%

“…The ring is fixed in the stretching device (see Fig. 1) in a position (7) between the supporting steel tube (8) and steel tube (9) that is stretched by the force F applied to the calibrated spring (10). The uniaxial compression of samples was calibrated in dependence on F by X-ray diffraction measurements [7].…”

Section: Samples and Experimental Setupmentioning

confidence: 99%

Electroluminescence in quantum well heterostructures p‐Al_xGa_1–xAs/GaAs_1–yP_y/n‐Al_xGa_1–xAs under uniaxial stress

Berman

Physica Status Solidi (b)

Kissel

et al. 2009

This article summarizes some of the key findings of a report (HM Inspectorate of Probation, 1998) of an inspection of the work of the probation service in England and Wales with sex offenders. The inspection took place at a time of unprecedented public debate and concern about the nature and impact of sexual offending, but this focused attention on a few high‐profile individuals rather than the majority of sexual offenders who assaulted victims that were known to them. For the purposes of the inspection, 10 probation areas were visited at the beginning of 1997 and a similar inspection programme was followed in each area, comprising observation of group work, examination of over 300 pre‐sentence court reports, a similar number of case files on offenders subject to supervision on probation orders and following release from prison and interviews with probation staff and representatives from a variety of other agencies. Although there had been research relating to community‐based probation programmes previously in this country, this concentrated on group work programmes, which, in reality, are attended by a minority of sex offenders under supervision. This inspection examined and assessed for the first time a far broader spectrum of the work of probation officers with sex offenders. Copyright © 1998 John Wiley & Sons, Ltd.