Ding-Kang Shih

Nitrogen-induced enhancement of the electron effective mass in InNxAs1-x

The electron effective mass in n-type InNxAs1−x (with x up to 3.0%) grown by gas-source molecular-beam epitaxy was obtained from infrared reflectivity and Hall-effect measurements. The large increase of the effective mass due to the incorporation of nitrogen is attributed mainly to the nitrogen-induced modification on the electronic states near the conduction-band edge. The well-known band anticrossing (BAC) model for the electronic structure of the III-N-V alloys cannot well describe the experimental data, especially in the region of higher electron concentration. This result provides an opportunity to examine the “universality” of the BAC model.

Shubnikov-de Haas oscillations of two-dimensional electron gas in an InAsN/InGaAs single quantum well

We present the first investigation of Shubnikov–de Haas (SdH) oscillations of two-dimensional electron gas formed in an InAsN/InGaAs single quantum well (QW) grown on an InP substrate using gas source molecular beam epitaxy and a radio-frequency (rf) plasma nitrogen source. The photoluminescence (PL) peak energy of the InAsN/InGaAs QW decreases compared with that of InAs/InGaAs QW. This agrees with the bowing effect due to the incorporation of nitrogen atoms. The nitrogen content can be estimated to be 0.4% using the PL peak positions as well as x-ray diffraction. From the SdH oscillations ,t he carrier concentration is 2.85 × 10 11 cm −2 and the effective mass is 0.1 ± 0.01m0 .T he enhancement of the effective mass is mainly due to the incorporation of the nitrogen atoms in the InAs lattice, which is consistent with a recent study on InAsN bulk alloys. The large increase of the effective mass cannot be explained by the simple band anticrossing model. In addition, we observe a temperatureindependent magnetoresistivity at a critical magnetic field. Our analysis supports the fact that the value of the critical exponent in the quantum Hall effect is not universal.

Probing the electronic structures of III–V-nitride semiconductors by x-ray photoelectron spectroscopy

The electronic structures of III–V-nitride semiconductors, including InGaAsN, GaAsN, and InAsN grown by molecular beam epitaxy, were investigated by high-resolution x-ray photoelectron spectroscopy using synchrotron radiation beam and low energy Ar+ sputtering. The N(1s) core-level photoelectron spectra show a single peak with a binding energy (Eb)∼398.0 eV of N–Ga bonding for GaAsN sample. For the InAsN samples, a single N(1s) peak at Eb∼397.0 eV of N–In bonding is observed. For the InGaAsN samples, the N(1s) spectra exhibit two peaks with a major component corresponding to N–In bonding, and a minor one to N–Ga bonding. The integrated N(1s) intensity of N–In bonding has a higher value than that of N–Ga bonding, in spite of the lower mole fraction of In for the InGaAsN sample. The data indicate that N has a bonding configuration with In-rich nearest neighbors in the InGaAsN samples.

Optical properties of as-grown and annealed InAs(N)/InGaAsP strained multiple quantum wells

Optical and structural properties of as-grown and annealed InAs(N)/InGaAsP strained multiple quantum-well (MQW) structures grown by gas source molecular-beam epitaxy are investigated by photoluminescence (PL), double crystal x-ray diffraction, and photoconductivity spectroscopies. Properties of the as-grown and annealed MQW’s are studied and those of the InAs/InGaAsP MQW (C821) and the InAsN/InGaAsP MQW with the lowest nitrogen contents N=1.1% in the well (C822) are compared. For the C821 InAs/InGaAsP MQW with a very large total strain, a low energy shoulder, possibly induced by defects or impurities, can be seen in the low temperature PL spectrum, and a large density of nonradiative recombination centers is found. For nitrogen-containing MQW’s, the PL full width at half maximum and PL peak evolutions with increasing annealing temperature are influenced by the alloy inhomogeneities. The initial redshift of the PL peak after rapid thermal annealing means that the luminescence is dominated by As-rich region...

Photoluminescence characterization of midinfrared InNxAs1–x/In0.53Ga0.47As/InP multiquantum wells with various N contents

pare a series of samples which are nominally identical in structure but differ only in N content in the range 0–5%. The photoluminescence PL measurements were carried out in a liquid He cooled flow cryostat of which the temperature can be controlled from 5 to 300 K. The excitation for the PL measurements was provided by a high power cw diode laser 670 nm. The PL signal was collected in a backscattering geometry via CaF2 optics, dispersed by a 0.46-m grating monochromator, and then detected by a thermoelectrically cooled InGaAs detector using standard lock-in techniques. Figure 1 shows the PL spectra at low 5K and room 300 K temperatures, respectively, of three samples of differing N contents N = 0, N = 0.25%, and N = 5%. All the PL spectra are dominated by an emission band denoted as band A with wavelength longer than 2 m which is attributed to the near-band-edge transition of the QWs. The N-induced bowing effect in these structures is evidenced by the PL redshift with the increase of the N content. By observing the

Band gap reduction in InAsN alloy

We report the absorption and photoluminescence (PL) properties of InAsN alloys grown by gas source molecular beam epitaxy. A calculation based on the band anticrossing model was used to evaluate the Burstein-Moss effect and the band renormalization effect due to the high residual carrier density in the alloy and also the original band gap energy. It can be seen from our calculation that the broad linewidths of the PL spectra are due to the Burstein-Moss effect, and the high-energy edges of these spectra are consistent with the results from absorption measurements. The low-energy edges of PL spectra are also shown to be close to the calculated original band gap energy.

Bulk InAsN films grown by plasma-assisted gas source molecular beam epitaxy

The growth of InAsN alloys with various nitrogen contents on [100] InP substrates by using plasma-assisted gas source molecular beam epitaxy is reported. The structural, electrical and optical properties of the alloy film are also investigated by using DXRD, Hall, and FTIR measurements. We found that the fundamental absorption edge of InAsN, as compared to that of InAs, shifts to higher energy due to Burstein-Moss effect. A dramatic increase of the electron effective mass in a nitrogen-containing III-V alloy is also observed.

Photoluminescence properties of dilute nitride InNAs/InGaAs/InP multi-quantum wells for mid-infrared applications

We report the photoluminescence characterization of a series InNAs/InGaAs multi-quantum wells (MQWs) of various N content on InP substrates. The emission wavelength of these QWs can be tuned effectively by N content. However, the bowing effect is weaker than in GaNAs and GaInNAs. The optical properties of these hetero-structures are closely related to quality of the interface between the barriers and the QWs which is influenced by N content. Two effects of N in this material system have been clarified. On the one hand, the incorporation of N into InAs matrix is beneficial as far as the reduction of band-gap and the lattice constant are concerned. On the other hand, the PL efficiency increases dramatically with the increase of N content. Optimized design and growth could be achieved by trading off between these two effects.