Z.Z. Sun

Optical property of self-assembled GaInNAs quantum dots grown by solid source molecular beam epitaxy

Abstract Self-assembled GaInNAs/GaAs quantum dots (QDs) are promising structures for extending the emission wavelength of GaInNAs/GaAs quantum wells from 1.3 to 1.55xa0μm and beyond. We report herein the growth of GaInNAs/GaAs quantum dot samples of different deposited thickness by solid source molecular beam epitaxy using active nitrogen radicals generated by a radio frequency nitrogen plasma source. Images from atomic force spectroscopy reveal the increase of non-uniformity QDs size following the increase in the deposited thickness. Temperature-dependent photoluminescence (PL) measurements show PL line width shrinkage at low temperature suggests the relaxation of carriers into neighboring QD local-energy minimum. The low thermal activation energy of ∼72xa0meV, estimated from the temperature-dependent integrated PL intensity curve suggests the existence of non-radiative recombination centers that quench the luminescence intensity at higher temperature.

High-temperature operation of self-assembled GaInNAs/GaAsN quantum-dot lasers grown by solid-source molecular-beam epitaxy

Self-assembled GaInNAs∕GaAsN single layer quantum-dot (QD) lasers grown using solid-source molecular-beam epitaxy have been fabricated and characterized. Temperature-dependent measurements have been carried out on the GaInNAs QD lasers. The lowest obtained threshold current density in this work is ∼1.05kA∕cm2 from a GaInNAs QD laser (50×1700μm2) at 10°C. High-temperature operation up to 65°C was also demonstrated from an unbonded GaInNAs QD laser (50×1060μm2), with high characteristic temperature of 79.4K in the temperature range of 10–60°C.

Electrical properties of silicon- and beryllium-doped GaInP and (AlGa)InP grown by solid source molecular beam epitaxy

Abstract Silicon- and beryllium-doped Ga0.52In0.48P and (Al0.7Ga0.3)0.52In0.48P were grown by solid source molecular beam epitaxy using a valved phosphorus cracker cell. The electrical properties were investigated using van der Pauw–Hall and capacitance–voltage measurements at room temperature. The highest electron concentration obtained was 6.9×1018 and 2.1×1018xa0cm−3 for Silicon doped Ga0.52In0.48P and (Al0.7Ga0.3)0.52In0.48P, respectively. The highest hole concentration obtained was 1.1×1019 and 4.9×1018xa0cm−3 for beryllium-doped Ga0.52In0.48P and (Al0.7-Ga0.3)0.52In0.48P, respectively. The Hall electron mobilities of Si-Ga0.52In0.48P and Si-(Al0.7Ga0.3)0.52In0.48P within the carrier concentration range of 1017

Self-assembled GaInNAs/GaAs quantum dots grown by solid-source molecular beam epitaxy

Abstract GaInNAs/GaAs quantum dots (QDs) were grown by solid-source molecular beam epitaxy equipped with a radio frequency nitrogen (N 2 ) plasma source for the first time. High-density (∼10 10 xa0cm −2 ) GaInNAs QDs with small sizes (∼30xa0nm) were achieved. Reflection high-energy electron diffraction observation revealed that the formation of GaInNAs QDs follows the Stranski–Krastanow growth mode. The evolution of GaInNAs QDs was investigated by atomic force microscopy, and the amount of GaInNAs coverage was found to have a significant effect on the dot density, average size and aspect ratio. Low temperature (5xa0K) photoluminescence measurement on the GaInNAs QDs showed that the incorporation of N into InGaAs effectively reduced the emission energy, and there is an optimal amount of GaInNAs coverage, which will produce QDs with maximum luminescence intensity.

Self-assembled GaInNAs/GaAsN quantum dot lasers: solid source molecular beam epitaxy growth and high-temperature operation

Self-assembled GaInNAs quantum dots (QDs) were grown on GaAs (001) substrate using solid-source molecular-beam epitaxy (SSMBE) equipped with a radio-frequency nitrogen plasma source. The GaInNAs QD growth characteristics were extensively investigated using atomic-force microscopy (AFM), photoluminescence (PL), and transmission electron microscopy (TEM) measurements. Self-assembled GaInNAs/GaAsN single layer QD lasers grown using SSMBE have been fabricated and characterized. The laser worked under continuous wave (CW) operation at room temperature (RT) with emission wavelength of 1175.86 nm. Temperature-dependent measurements have been carried out on the GaInNAs QD lasers. The lowest obtained threshold current density in this work is ∼1.05 kA/cm2from a GaInNAs QD laser (50 × 1,700 µm2) at 10 °C. High-temperature operation up to 65 °C was demonstrated from an unbonded GaInNAs QD laser (50 × 1,060 µm2), with high characteristic temperature of 79.4 K in the temperature range of 10–60 °C.

Mechanism of emission-energy tuning in InAs quantum dots using a thin upper confinement layer

The emission-energy tuning mechanism in InAs quantum dots using a thin upper confinement layer (UCL) was investigated. By comparing the emission-energy tuning ability of InGaP and InGaAs UCLs in InAs/UCL dot structures, strain adjustment rather than mass transport was identified as the dominant mechanism responsible for emission-energy tuning in the InAs quantum dots. An explanation of the general emission-energy tuning behavior by the UCL was given based on strain adjustment mechanism.

Some properties of carbon-doped GaAs using carbon tetrabromide in solid-source molecular beam epitaxy

Abstract Heavily carbon-doped (C-doped) GaAs epitaxial films with hole concentration up to 1.86×10 20 xa0cm −3 have been grown using carbon tetetrabromide (CBr 4 ) as dopant source in solid-source molecular beam epitaxy (SSMBE). The hole concentration decreases at concentration beyond 1.86×10 20 xa0cm −3 due to compensation by carbon–carbon (C–C) pairs. At room temperature, the C-doped samples showed mobility of 77–60xa0cm 2 /Vxa0s at hole concentration of 2.79×10 19 –1.09×10 20 xa0cm −3 , respectively, comparable to samples doped with beryllium (Be). Low temperature (4xa0K) photoluminescence (PL) measurements show a reduction in band gap and broadening of the PL spectrum following increase in the doping concentration. The main PL peak shifts from ∼1.480xa0eV at concentration of 1.02×10 19 xa0cm −3 to ∼1.452xa0eV at 6.95×10 19 xa0cm −3 . Variable temperature PL measurements show the existence of two peaks, which could arise from conduction band (CB) to heavy hole (HH) valence band and CB to light hole (LH) valence band transitions. Doping pulses created using CBr 4 flux resulted in abrupt transitions in the C-doping profile. Good agreement between the atomic concentration measured by secondary ion mass spectroscopy (SIMS) and the hole carrier concentration measured by Hall effect was observed up to doping level of 1.6×10 20 xa0cm −3 .

GaInP/GaAs heterojunction bipolar transistor with carbon-doped base layer grown by solid source molecular beam epitaxy using carbon tetrabromide

Abstract This paper reports the growth of GaInP/GaAs heterojunction bipolar transistor (HBT) with carbon-doped GaAs (GaAs:C) base layer grown by solid source molecular beam epitaxy using carbon tetrabromide (CBr 4 ) as p-type dopant precursor. HBT devices with base layer thickness of 520 A showed DC current gain of 30 at collector current density of 3200 A/cm 2 . The majority carrier mobility at room temperature obtained from the base layer sheet resistance is consistent with that of carbon-doped GaAs bulk layer, indicating reasonable control of the carbon doping in the base layer of the HBT structure. The device properties within temperature range from 300 to 380 K were investigated. The temperature dependence of DC current gain vs. collector current showed a slight decrease of β at high collector current and increase of β at low collector current. The Gummel plot from 300 to 380 K suggests that the effect of trap-related recombination is dominant.

Carbon doping in GaAs using carbon tetrabromide in solid source molecular beam epitaxy

Abstract Carbon tetrabromide (CBr4) has been used as a source of p-type dopant in GaAs (GaAs:C) grown by solid source molecular beam epitaxy (SSMBE). The stability and sustainability of the CBr4 flux were investigated in terms of the leak valve position and CBr4 cylinder temperature. It is found that stable and sustainable CBr4 flux ranging from ∼2.0×10−8 to ∼1×10−6xa0Torr can be obtained by regulating the leak valve opening position within cylinder temperature of 2–20°C. The hole concentration in GaAs increases linearly following increase in CBr4 flux up to 2.6×10−7xa0Torr, at which the hole concentration is the highest at 1.86×1020xa0cm−3. Thereafter, the hole concentration decreases due to formation of electrically inactive C–C pairs. The memory effect in GaAs from possible background carbon doping was found to be at an acceptably low level of ∼1015xa0cm−3 hole concentration, indicating the viability of CBr4 usage in SSMBE for p-type doping.

Comparison of Characteristic Temperature from Triple quantum Well and Single Quantum Well GaInNAs Ridge Waveguide Lasers

GaInNAs triple quantum well (TQW) and single quantum well (SQW) lasers have been fabricated and compared. The TQW GaInNAs lasers showed much higher characteristic temperature than that of SQW GaInNAs lasers with the same dimension.