A study of dilute nitride-antimonide semiconductors for near infrared optoelectronics devices

In this thesis, GaNAsSb-based optoelectronic device structures were grown using a solid-source molecular beam epitaxy (MBE) system in conjunction with a radio frequency (RF) plasma N source and Sb valved-cracker source. To reduce the nitrogen plasma induced defects, an ion deflection plate has been installed. Four p-i-n GaNAsSb-based photodetectors have been grown using MBE for photoresponsivity measurement. The devices have shown photo-response up to a wavelength of 1380nm in the spectral response. The device with GaNAsSb layer grown at 350oC shows the highest DC responsivity of 12A/W. This high value of responsivity indicates a carrier avalanche process in the devices, even at reverse bias as low as 1V. In temporal response measurement, the device shows a pulse minimum full-width at half maximum (FWHM) of 40.5ps, corresponding to 3dB cutoff frequency of 4.5GHz. This frequency response is the highest ever reported for dilute nitride-based p-i-n photodetector. Furthermore, high speed data transmission at 5Gb/s has been demonstrated using this GaNAsSb-based p-i-n photodetector at wavelength of 1300nm. To further extend the photo-response from 1380nm to 1600nm, a GaNAsSb-based p-i-n waveguide photodetector has been grown using the molecular beam epitaxy. The device consists of a strained GaNAsSb photon-absorption layer, which has 3.5% of N and 18% of Sb. The device shows photo-response up to at least 1600nm in the spectral response. Moreover, photoresponsivity of 0.29A/W of the device at 1550nm was demonstrated.DOCTOR OF PHILOSOPHY (EEE

Characterisation of a diamond-like carbon deposition process

Diamond-like carbon (DLC) films have attracted great interest in several applications in optical and tribological systems, and field emission displays due to its unique properties such as, high optical transparency in the infrared (IR) region, low electron affinity and high chemical inertness. In this project, DLC films have been deposited using the Electron Cyclotron Resonance Chemical Vapor Deposition (ECR-CVD) technique.Master of Engineerin

Growth of InAs0.32Sb0.68on GaAs using a thin GaInSb buffer and strain superlattice layers

10.1063/5.0045483AIP Advances11404520

Growth of droplet-free InSbBi on GaAs substrate

Indium antimonide bismide (InSbBi) has emerged as a highly promising material for long-wavelength infrared photodetection devices due to its unique small energy bandgap (<0.17 eV) compared to existing III–V compound semiconductors. Despite its potential, experimental studies on InSbBi are still incomplete and scarce. Furthermore, the challenges associated with incorporating Bi and producing high-quality, defect-free samples are yet to be adequately addressed. To tackle these issues, we systematically investigated the growth of InSbBi on a GaAs substrate in this study. We incorporated up to 3.4% of Bi into InSbBi material. Our research contributes significantly to the field by demonstrating a technique for growing high-quality InSbBi material with Bi content of up to 2.3%, which is free of droplets and features a smooth surface. We achieved this goal by dynamically adjusting the Sb flux, carefully controlling the interplay between the Bi flux and the growth temperature, and implementing a post-growth annealing process. Our work is crucial for developing InSbBi technology as it contributes to the understanding of the growth process and surface morphology of InSbBi. Moreover, our results provide a path toward producing high-quality InSbBi samples

Effect of N incorporation on the characteristics of InSbN P–N diodes

We report on the effect of N incorporation in the characteristics of the 2 μm thick InSbN photoabsorption layer of a p–n diode grown by molecular beam epitaxy using a radio-frequency plasma-assisted nitrogen source. As compared to N free InSb layer, the absorption wavelength extends to near 9 μm. On the other hand, high reverse dark current and series resistances are observed in the electrical characteristics of the InSbN diode which are contributed with the presence of planar growth defects. These results will be useful to those working on midinfrared photodetectors

Structural Behaviour of Precast Beam-Column Sub-Assemblages with Cast-In-Situ Engineered Cementitious Composites under Column Removal Scenarios

This paper presents an experimental study on the structural behaviour of precast beam-column sub-assemblages under column removal scenarios, in which conventional concrete and engineered cementitious composites (ECC) were used in the cast-in-situ concrete topping and the beam-column joint. The specimens were restrained by horizontal and vertical load cells and tested under quasi-static loading condition. Experimental results indicate that at the initial stage ECC and steel reinforcement sustained tensile stresses compatibly and multiple cracking was observed in the ECC topping. When the tensile strain capacity of ECC was exhausted, major cracks were formed in the plastic hinge region, whereas at other sections ECC remained intact to transfer tensile stresses across cracks. Compared to conventional concrete, ECC resulted in more severe localisation of rotations in a limited region due to its tension-stiffening behaviour. Conclusions are drawn that application of ECC to structural topping and beam-column joints did not significantly enhance structural resistance of sub-assemblages under column removal scenarios. However, the calculated pseudo-static resistance of ECC sub-assemblage is greater than that of concrete specimen due to better energy-absorption capacity of ECC.Accepted versio

Effect of in situ annealing on the structural and electrical properties and infrared photodetection of III-Sb on GaAs using interfacial misfit array

This work presents the effects of in situ thermal annealing under antimony overpressure on the structural, electrical, and optical properties of III-Sb (GaSb and InSb) grown on (100) GaAs using an interfacial misfit array to accommodate the lattice mismatch. Both the sample growth and the in situ thermal annealing were carried out in the in the molecular beam epitaxy system, and the temperature of the as-grown sample was increased to exceed its growth temperature during the annealing. X-ray diffraction demonstrates nearly fully relaxed as-grown and annealed III-Sb layers. The optimal annealing temperatures and durations are for 590 °C, 5 min for GaSb and 420 °C, 15 min for InSb, respectively. In situ annealing decreased the surface roughness of the III-Sb layers. X-ray reciprocal space mapping and transmission electron microscopy observation showed stable interfacial misfit arrays, and no interfacial diffusion occurred in the annealed III-Sb layers. A Hall measurement of unintentionally doped III-Sb layers showed greater carrier mobility and a lower carrier concentration in the annealed samples at both 77 and 300 K. In situ annealing improved the photoresponsivity of GaSb and InSb photoconductors grown on GaAs in the near- and mid-infrared ranges, respectively.NRF (Natl Research Foundation, S’pore)Accepted versio

Epitaxial growth of low threading dislocation density InSb on GaAs using self-assembled periodic interfacial misfit dislocations

We report a fully relaxed low threading dislocation density InSb layer grown on a GaAs substrate using self-assembled periodic interfacial misfit dislocations. The InSb layer was grown at 310°C by molecular beam epitaxy. The AFM measurement exhibited a root mean square (r.m.s.) roughness of 1.1 nm. ω-2θ scan results from x-ray diffraction measurement indicated that the InSb layer is 98.9% relaxed. Images from the transmission electron microscope measurement showed a threading dislocation density of 1.38×108 cm-2. The formation of highly uniform interfacial misfit dislocation array was also observed and the separation of dislocations is consistent with theoretical calculation. The InSb layer exhibited a 33,840 cm2/V s room temperature electron mobility.NRF (Natl Research Foundation, S’pore)Accepted versio

Growth and characterization of an InSb infrared photoconductor on Si via an AlSb/GaSb buffer

A 99.6% relaxed InSb layer is grown on a 6° offcut (1 0 0) Si substrate via an AlSb/GaSb buffer using molecular beam epitaxy (MBE). A 200 nm GaSb buffer is first grown on Si and the lattice mismatch between them is accommodated by an interfacial misfit (IMF) array consisting of uniformly distributed 90° misfit dislocations. Si delta doping is introduced during the growth of GaSb to reduce the density of threading dislocation. Subsequently, a 50 nm AlSb buffer is grown followed by a 0.8 µm InSb layer. The InSb layer exhibits a 300 K electron mobility of 22,300 cm2/Vs. An InSb photoconductor on Si is demonstrated with a photoconductive gain from 77 K to 200 K under a 700 °C maintained blackbody.NRF (Natl Research Foundation, S’pore)Accepted versio