N. Hossain

Laser operation of Ga(NAsP) lattice-matched to (001) silicon substrate

The lattice-matched growth of the direct band gap material Ga(NAsP) is a seminal concept for the monolithic integration of III/V laser on a silicon substrate. Here, we report on the growth, characterization, and lasing properties of Ga(NAsP)/(BGa)(AsP) multi quantum well heterostructures embedded in (BGa)P cladding layers which were deposited on an exactly oriented (001) Si substrate. Structural investigations confirm a high crystal quality without any indication for misfit or threading dislocation formation. Laser operation between 800 nm and 900 nm of these broad area device structures was achieved under optical pumping as well as electrical injection for temperatures up to 150 K. This “proof of principle” points to the enormous potential of Ga(NAsP) as an optical complement to Si microelectronics.

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.

Band structure properties of novel BxGa1−xP alloys for silicon integration

We have grown and investigated the band-structure properties of novel III-V alloys based upon BxGa1−xP. These layers are utilized as strain-compensating layers for the lattice-matched integration of novel direct bandgap Ga(NAsP) quantum well lasers on silicon. Experimental and theoretical studies reveal the dependence of the direct and indirect band gaps for strained BxGa1−xP layers grown on silicon as a function of Boron composition from which we derive the properties of free-standing BxGa1−xP. For Boron fractions up to 6%, we find that the bowing parameter for the lowest (indirect) band gap is − 6.2 ± 0.2 eV. High crystalline quality and promising optical material properties are demonstrated and applied to monolithically integrated Ga(NAsP)/(BGa)P multi-quantum well heterostructures on (001) silicon substrates. Our results show that novel (BGa)P layers are suitable for strain compensation purposes, which pave the way towards a commercial solution for the monolithic integration of long term stable laser ...

Improved Performance of GaAsSb/GaAs SQW Lasers

This paper reports the improvements and limitations of MBE grown 1.3μm GaAsSb/GaAs single QW lasers. At room temperature, the devices show a low threshold current density (Jth) of 253 Acm-2, a transparent current density of 98 Acm-2, an internal quantum efficiency of 71%, an optical loss of 18 cm-1 and a characteristic temperature (T0) = 51K. The defect related recombination in these devices is negligible and the primary non-radiative current path has a stronger dependence on the carrier density than the radiative current contributing to ~84% of the threshold current at RT. From high hydrostatic pressure dependent measurements, a slight decrease followed by the strong increase in threshold current with pressure is observed, suggesting that the device performance is limited to both Auger recombination and carrier leakage.

Physical Properties and Characteristics of III-V Lasers on Silicon

The development of laser technology based on silicon continues to be of key importance for the advancement of electronic-photonic integration offering the potential for high data rates and reduced energy consumption. Progress was initially hindered due to the inherent indirect band gap of silicon. However, there has been considerable progress in developing ways of incorporating high gain III-V based direct band gap materials onto silicon, bringing about the advantages of both materials. In this paper, we introduce the need for lasers on silicon and review some of the main approaches for the integration of III-V active regions, including direct epitaxial growth, hybrid integration, defect blocking layers and quantum dots. We then discuss the roles of different carrier recombination processes on the performance of devices formed using both wafer fusion and direct epitaxial approaches.

Hybrid Silicon Devices for Energy-Efficient Optical Transmitters

Decreasing energy limits for data transport have resulted in efforts to reduce energy consumption in optical interconnects. The authors introduce three possible integration techniques for realizing a hybrid silicon transmitter on a single chip with distributed feedback (DFB) lasers and electro-absorption modulators. They review the current bottlenecks and techniques for further reducing threshold current and increasing the wall-plug efficiency of these lasers.

Efficiency-limiting processes in Ga(NAsP)/GaP quantum well lasers

We report on the carrier recombination mechanisms in dilute nitride Ga(NAsP)/GaP quantum well lasers. Spontaneous emission measurements show that defect-related recombination in the devices is less significant compared with other GaAs-based dilute nitride lasers. From temperature dependent measurements, we find that the threshold current density, Jth is dominated by non-radiative recombination process(es), which account for at least 91% of Jth at room temperature. The characteristic temperature, T0 (T1) is measured to be ∼104 K (∼99 K) around 200 K, which drops to ∼58 K ( ∼37 K) around room temperature. Hydrostatic pressure measurements reveal a strong increase of threshold current with increasing pressure. This implies that current leakage dominates carrier recombination which is also responsible for their low T0 and T1 values at room temperature.

MOVPE growth and characterization of Ga(NAsP) laser structures monolithically integrated on Si (001) substrates

Laser structures containing the dilute nitride material Ga(NAsP) can be grown lattice matched on silicon substrates with high crystal quality and low defect density. Lasing operation from broad area lasers up to 120K is verified.