The short-wavelength edge of intrinsic photoluminescence in diluted GaN x As1 − x alloys (original) (raw)

Intensity dependence of photoluminescence in GaN thin films

Applied Physics Letters, 1994

We report the intensity dependence of band-gap and midgap photoluminescence in GaN films grown by electron cyclotron resonance (ECR) microwave plasma-assisted molecular beam epitaxy. We find that the band-gap luminescence depends linearly while the midgap luminescence has a nonlinear dependence on the incident light intensity. These data were compared with a simple recombination model which assumes a density of recombination centers 2.2 eV below the conduction band edge. The concentration of these centers is higher in films grown at higher microwave power in the ECR plasma.

Optical characterisation of GaN and related materials

Solid-State Electronics, 1997

Recent experimental results on optical properties of GaN and related materials are discussed. Photoluminescence data of free excitons for sufficiently pure GaN samples demonstrate the dominance of excitonic recombination well above room temperature. Transient PL data give a radiative lifetime of about 200 ps for the A-exciton at 2 K in strain-free samples. A corresponding value of about 2 ns at room temperature is extrapolated. Radiative lifetimes for bound excitons are measured as about 250 ps for shallow donors and about 1.5 ns for shallow acceptors. Photoluminescence spectra from the 2D electron gas at a GaN/AIGaN heterointerface are also demonstrated.

Photoluminescence of residual transition metal impurities in GaN

Applied Physics Letters, 1995

A large number of epitaxial GaN samples as well as AlN ceramics have been studied by photoluminescence ͑PL͒ and PL excitation spectroscopy. In addition to the PL of residual iron, two new bands with zero-phonon-lines at 0.931 and 1.193 eV have been observed frequently in GaN. An analysis of the PL bands indicates that they arise from internal transitions within the 3d shell of residual vanadium and chromium impurities. The chromium PL has also been observed in polycrystalline AlN ceramics.

Broadening of near-band-gap photoluminescence in n-GaN films

Applied Physics Letters, 1998

This letter addresses the broadening mechanism of the near-band-gap photoluminescence in GaN films doped n type with silicon. The films were produced by plasma assisted molecular beam epitaxy and their carrier concentration was varied systematically from 10 15 to 10 20 cm Ϫ3 . The photoluminescence was excited with a 10 mW He-Cd laser at 77 K. At low carrier concentration (Ͻ10 17 cm Ϫ3 ) the photoluminescence peak has a full width at half maximum of about 18 meV, while at high carrier concentration (Ͼ10 18 cm Ϫ3 ) the full width at half maximum increases monotonically with carrier concentration up to about 120 meV. The broadening of the line at high carrier concentration is attributed to tailing of the density of states caused by potential fluctuations due to randomly distributed impurities. The data were quantitatively analyzed, as a function of carrier concentration and compensation ratio, using the impurity band broadening model of Morgan ͓Phys. Rev. 139, A343 ͑1965͔͒, and the agreement between model and experimental data supports the model's validity and suggests a potential method of determining the compensation in degenerate nitride semiconductors.

Photoluminescence Excitation Studies of the Optical Transitions in GaN

MRS Proceedings, 1996

ABSTRACTWe present a detailed photoluminescence excitation study of the optical transitions in GaN. This technique is employed to distinguish between band-to-band excitation and exciton contribution to the formation of the free exciton, bound exciton, violet and yellow photoluminescence bands. We show the dominant role of the Fröhlich polar intraband scattering in the formation of the free exciton states. We demonstrate that bound exciton states in a large extent are created by the capture of the free excitons by shallow impurities as well as by phononassisted resonant excitation of the bound exciton states. The capture of the free carriers excited in the band continuum is a main excitation source for the violet and yellow bands. However, distinct A- and C-exciton resonances are detected in the excitation spectra of the violet and yellow emission bands.

The electron effective mass at the bottom of the GaNAs conduction band

Semiconductor Science and Technology, 2004

We determined the electron effective mass, m * e , from the photoluminescence (PL) of GaN x As 1−x /GaAs single quantum wells. The energy of the interband optical transitions is analysed within the frame of the band anti-crossing model (BAC), which accounts for a highly nonparabolic nature of the GaNAs conduction band (CB). From the PL we found that m * e at the bottom of the CB in GaN x As 1−x /GaAs quantum wells (QWs) increases from 0.095m 0 to 0.12m 0 for x increasing from 0.009 to 0.04. We found that the BAC model for III-N-V QWs predicts a strong increase of m * e as a function of the electronic subband number. We analyse also m * e at the bottom of the bulk GaNAs CB using the linear-muffin-tin-orbital (LMTO) method adjusted by inclusion of external potentials to account properly for energy gaps. The effective mass dependence obtained from LMTO calculations reproduces the experimental results. The nature of the nitrogen related A 1 symmetry state, which enters in the BAC model, and similarities of this state with the Ga dangling bond state are discussed.

Photoluminescence Spectroscopy of Band Gap Shrinkage in GaN

Arxiv preprint cond-mat/0604221, 2006

We present an experimental investigation of band-gap shrinkage in n-type GaN using photoluminescence spectroscopy, as a function of electron concentration and temperature. The observed systematic shift of the band-to-band transition energy to lower energies with increasing electron concentration has been interpreted as many-body effects due to exchange and correlation among majority and minority carriers. The band-to-band transition energy also shifts to lower energy with increasing temperature. The parameters that describe the temperature dependence red-shift of the band-edge transition energy are evaluated using different models and we find that the semiempirical relation based on phonon-dispersion related spectral function leads to excellent fit to the experimental data.