S. R. Jin

Bismide-nitride alloys: Promising for efficient light emitting devices in the near- and mid-infrared

GaAsBiN is a potentially interesting alloy which may be exploited in near- and mid-infrared photonic devices. Here we present the predicted band parameters such as band gap (Eg), the spin-orbit splitting energy (ΔSO), band offsets and strain of GaAsBiN on GaAs versus N and Bi compositions based on recent experimental data. We also show how bismuth may be used to form alloys whereby ΔSO > Eg thereby providing a means of suppressing non-radiative CHSH (hot-hole producing) Auger recombination and inter-valence band absorption. We determine the optimum conditions where ΔSO > Eg, which is expected to improve the high-temperature performance and thermal stability of light emitting devices. It is also shown that preferential band offsets are achievable with GaAsBiN, which makes this material system promising for photonic devices operating in the near- and mid-infrared.

Electrical injection Ga(AsBi)/(AlGa)As single quantum well laser

The Ga(AsBi) material system opens opportunities in the field of high efficiency infrared laser diodes. We report on the growth, structural investigations, and lasing properties of dilute bismide Ga(AsBi)/(AlGa)As single quantum well lasers with 2.2% Bi grown by metal organic vapor phase epitaxy on GaAs (001) substrates. Electrically injected laser operation at room temperature is achieved with a threshold current density of 1.56 kA/cm2 at an emission wavelength of ∼947 nm. These results from broad area devices show great promise for developing efficient IR laser diodes based on this emerging materials system.

Recombination mechanisms and band alignment of GaAs1-xBix/GaAs light emitting diodes

We investigate the temperature and pressure dependence of the light-current characteristics and electroluminescence spectra of GaAs1−xBix/GaAs light emitting diodes. The temperature dependence of the emission wavelength shows a relatively low temperature coefficient of emission peak shift of 0.19 ± 0.01 nm/K. A strong decrease in emission efficiency with increasing temperature implies that non-radiative recombination plays an important role on the performance of these devices. The pressure coefficient of the GaAs0.986Bi0.014 bandgap is measured to be 11.8 ± 0.3 meV/kbar. The electroluminescence intensity from GaAsBi is found to decrease with increasing pressure accompanied by an increase in luminescence from the GaAs cladding layers suggesting the presence of carrier leakage in the devices.

Temperature and Bi-concentration dependence of the bandgap and spin-orbit splitting in InGaBiAs/InP semiconductors for mid-infrared applications

Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, Eg, and spin-orbit splitting, ΔSO, respectively. The possibility of achieving ΔSO > Eg and a reduced temperature (T) dependence for Eg are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure Eg(x, T) and ΔSO (x, T) in In0.53Ga0.47BixAs1−x/InP samples for 0 ≤ x ≤ 0.039 by various complementary optical spectroscopic techniques. While we find no clear evidence of a decreased dEg/dT (≈0.34 ± 0.06 meV/K in all samples) we find ΔSO > Eg for x > 3.3–4.3%. The predictions of a valence band anti-crossing model agree well with the measurements.

Physical properties and optimization of GaBiAs/(Al)GaAs based near-infrared laser diodes grown by MOVPE with up to 4.4% Bi

This paper reports on progress in the development of GaAsBi/(Al)GaAs based lasers grown using metal-organic vapour phase epitaxy and focuses on the underlying processes governing their efficiency and temperature dependence. Room temperature lasing has been achieved in devices with 2.2% Bi and lasing in devices with 4.4% Bi was observed up to 180 K. We show that the device performance can be improved by optimizing both electrical and optical confinement in the laser structures. Analysis of the temperature dependence of the threshold current together with pure spontaneous emission and high hydrostatic pressure measurements indicate that device performance is currently dominated by non-radiative recombination through defects (>80% of the threshold current at room temperature in 2.2% Bi samples) and that to further improve the device performance and move towards longer wavelengths for optical telecommunications (1.3–1.5 µm) further effort is required to improve and optimize material quality.

The potential role of Bismide alloys in future photonic devices

In a similar manner to the dilute nitrides, the incorporation of Bismuth in semiconductors such as GaAs is predicted to lead to a band-anti-crossing effect (in the valence band) causing a large band gap bowing. In addition, the large size of Bismuth atoms gives rise to a large spin-orbit splitting. This opens-up interesting new possibilities for efficient photonic devices, such as near- and mid-infrared lasers which are more thermally stable and less susceptible to losses compared to conventional InP-based devices. Since Bismuth principally influences the valence band, while nitrogen influences the conduction band, combining Bismuth and Nitrogen in III–V alloys offers huge potential for engineering the conduction and valence band offsets, the band gap and spin-orbit splitting, with wide scope for the design of photonic devices.

Properties of hybrid MOVPE/MBE grown GaAsBi/GaAs based near-infrared emitting quantum well lasers

A combined growth approach involving both molecular-beam epitaxy and metal-organic vapor phase epitaxy has been developed to fabricate GaAsBi/GaAs-based quantum well (QW) laser structures with a Bi composition up to 8%. Lasing operation has been demonstrated at room temperature at 1.06 μm in laser diodes containing 3QWs that in turn contain approximately 6% Bi. A 5QW device demonstrated lasing at 1.09 μm at 80 K. Using temperature- and pressure-dependent measurements of stimulated emission as well as pure spontaneous emission measurements, we show that the threshold current of the devices is limited by non-radiative defect-related recombination and an inhomogeneous carrier distribution. This is suspected to be due to inhomogeneity of the QW width as well as non-uniform Bi composition in the active region.

High-pressure studies of recombination mechanisms in 1.3-/spl mu/m GaInNAs quantum-well lasers

The pressure dependence of the components of the recombination current at threshold in 1.3-/spl mu/m GaInNAs single quantum-well lasers is presented using for the first time high-pressure spontaneous emission measurements up to 13 kbar. It is shown that, above 6 kbar, the rapid increase of the threshold current with increasing pressure is associated with the unusual increase of the Auger-related nonradiative recombination current, while the defect-related monomolecular nonradiative recombination current is almost constant. Theoretical calculations show that the increase of the Auger current can be attributed to a large increase in the threshold carrier density with pressure, which is mainly due to the increase in the electron effective mass arising from the enhanced level-anticrossing between the GaInNAs conduction band and the nitrogen level.

Unusual increase of the Auger recombination current in 1.3 μm GaInNAs quantum-well lasers under high pressure

The pressure dependence of the total threshold current and its respective recombination components in 1.3 μm GaInNAs single-quantum-well lasers using spontaneous emission measurements up to 13 kbar is presented. We observed an unusual increase of the nonradiative Auger recombination current with increasing pressure in this material, which is opposite to those in 1.3 μm InP-based InGaAsP and AlGaInAs devices where the Auger current decreases with pressure. It is shown that the high-pressure-induced increase of the threshold current in GaInNAs is associated with the increase of the Auger current, while the defect-related monomolecular nonradiative current remains nearly unchanged in the pressure range studied. Theoretical calculations show that the unusual increase of the Auger current with pressure in GaInNAs is due to a large increase in the threshold carrier density.

Enhancement of Rashba interaction in GaAs/AlGaAs quantum wells due to the incorporation of bismuth

This paper reports on the predicted increase in the Rashba interaction due to the incorporation of Bi in GaAs/AlGaAs heterostructures. Band structure parameters obtained from the band anti-crossing theory have been used in combination with self-consistent Schrodinger-Poisson calculations and k.p models to determine the electron spin-splitting caused by structural inversion asymmetry and increased spin-orbit interaction. A near linear seven fold increase in the strength of the Rashba interaction is predicted for a 10% concentration of Bi in a GaAsBi/AlGaAs quantum well heterostructure.