Kian Hua Tan

Effects of nitrogen incorporation in InSb1−xNx grown using radio frequency plasma-assisted molecular beam epitaxy

InSb1−xNx was grown by radio frequency plasma-assisted molecular beam epitaxy. The effect of nitrogen plasma power (200–500W) and growth temperature (330–420°C) on nitrogen incorporation was investigated. A combined analysis involving x-ray diffraction, x-ray photoelectron spectroscopy, and secondary ion mass spectroscopy measurements indicates that the dominant nitrogen defect is interstitial N–Sb. Increasing the plasma power resulted in increase in the interstitial N–Sb amount rather than the substitutional NSb amount. For fixed plasma power, decreasing the growth temperature helped reduce the interstitial N–Sb defect. Under the experimental conditions, the average value of substitutional N is approximately 1.6%–2%.

Modeling and analysis of hydrogen–methane plasma in electron cyclotron resonance chemical vapor deposition of diamond-like carbon

Diamond-like carbon films were deposited using the electron cyclotron resonance chemical vapor deposition (ECR-CVD) system. A model for the ECR plasma was formulated using deposition parameters, such as microwave power, pressure, and hydrogen/methane ratio as inputs. Using the model, electron energy, rate constant of electron impact reactions, and density of species in the plasma are calculated. The outputs of the model are analyzed as a function of deposition conditions, such as microwave power, pressure, and hydrogen/methane ratio and compared to experimental data measured using a Langmuir probe. The results show that ion density increases following the increase in microwave power and hydrogen/methane ratio, and decreases following the increase pressure. Results from the model are in agreement with experimental data, and show that the main neutral species are H2, CH4, H, CH3, CH, C2H5, CH2, and C2H6. The main ionic species are H2+, CH4+, CH3+, CH2+, H+, CH5+, C2H4+, C2H5+, and CH+.

High-speed picosecond pulse response GaNAsSb p-i-n photodetectors grown by rf plasma-assisted nitrogen molecular beam epitaxy

The authors report on picosecond pulse response GaNAsSb∕GaAs p-i-n photodetectors grown by molecular beam epitaxy in conjunction with a rf plasma-assisted nitrogen source. The 2μm thick GaNAsSb photoabsorption layer contains 3.3% of N and 8% of Sb resulting in a dc photoresponse up to 1380nm wavelength. Dark current densities at 0 and −5V are 1.6×10−5 and 13A∕cm2, respectively. The GaNAsSb photodiodes exhibit a record pulse response width of only 40.5ps (full width at half maximum) corresponding to a 4.5GHz bandwidth.

Effect of growth temperature on defect states of GaAsSbN intrinsic layer in GaAs∕GaAsSbN∕GaAs photodiode for 1.3μm application

A GaAsSbN layer closely lattice matched to GaAs was used as an intrinsic layer (i layer) in a GaAs∕GaAsSbN∕GaAs p-i-n photodiode with response up to 1.3μm. Deep level transient spectroscopy measurement on the GaAs∕GaAsSbN∕GaAs reveals two types of hole traps (HTs) in the GaAsSbN i layer; (i) HT1: a shallow N-related defect state (Ea∼0.10–0.12eV) and (ii) HT2: an AsGa point defect-related midgap defect state with Ea∼0.42–0.43eV. Reduction in growth temperature from 480to420°C reduces the HT2 trap concentration from 4×1015to1×1015cm−3, while increases the HT1 trap concentration from 1×1014to7×1014cm−3. Reduction in the HT2 trap concentration following growth temperature reduction was attributed to the suppression of AsGa point defect formation. Evidence of possible change of the AsGa midgap state to a shallow level defect due to the formation of (AsGa–NAs) pairs was also suggested to have increased the HT1 trap concentration and reduced the HT2 trap concentration. An ∼4dBm improvement in photoresponse under...

Defect-induced trap-assisted tunneling current in GaInNAs grown on GaAs substrate

We present the reverse-bias current-voltage and deep-level transient spectroscopy (DLTS) characteristics of a Ga0.90In0.10N0.033As0.967∕GaAs positive-intrinsic-negative photodiode (Eg=0.92 eV) and a trap-assisted tunneling model which considers generation-recombination and tunneling mechanisms. Using trap parameters obtained from the DLTS measurement, the model generates current-voltage characteristics of the photodiode, which were found to be in good agreement with experimental current-voltage curves at different temperature. The model also suggests that high dark current at low reverse-bias voltage is caused by the presence of traps which have low activation energy. Furthermore, it is predicted that approximately ten times reduction in the dark current can be achieved when the trap concentration of type H-1 (Ea=0.15 eV) is reduced by one order. On the other hand, a similar reduction in defect concentration of type H-2 (Ea=0.40 eV), which is nearer to midgap does not produce the same effect.

Near-infrared photon upconversion devices based on GaNAsSb active layer lattice matched to GaAs

Room-temperature full GaAs-based near-infrared (NIR) upconversion has been demonstrated by connecting lattice-matched GaNAsSb/GaAs p-i-n photodetectors in series with commercial GaAs/AlGaAs light-emitting diodes (LEDs). Due to the avalanche gain in GaNAsSb/GaAs photodetectors and high internal efficiency in GaAs/AlGaAs LEDs, the upconversion efficiency of the integrated system reaches 0.048 W/W under −7 V bias, much higher than any existing NIR upconverters without amplifying structures. We have further investigated the dependence of the upconversion efficiency on applied bias and incident light intensity. The present work establishes an experimental base for direct epitaxial growth of full GaAs-based NIR upconverters with high upconversion efficiencies.

Dry Etched Waveguide Laser Diode on GeOI

We demonstrate a top-top contact, dry etched mirror facet III-V waveguide laser diode grown on germanium-on-insulator (GeOI). A 3 × InGaAs/GaAs quantum well designed to lase at 985 nm was grown on a GaAs buffer, which was lattice matched to the GeOI platform in order to realize the monolithic integration of III-V electronic and photonic devices with silicon and SiO2. Lasing occurred at ~ 985 nm with a threshold current density of ~ 2 kA/cm2. Pulsed measurements, and SEM and TEM characterization methods were used. The issue of heat transfer limited the performance of the laser.

Catalyzed growth of carbon nanoparticles by microwave plasma chemical vapor deposition and their field emission properties

Carbon nanoparticles were prepared from H2 and CH4 by microwave plasma chemical vapor deposition at various temperatures as low as 250 °C by using nickel and iron as catalysts. The carbon nanoparticles are well graphitized until a temperature as low as 400 °C, and the degree of graphitization increases with increasing growth temperature. Field emission measurements showed that the carbon nanoparticles are excellent electron field emitters, comparable to carbon nanotubes. Field emission properties became better with increasing growth temperature, and the threshold fields of the carbon nanoparticles deposited at 400, 500, 670 °C, were 3.2, 3, and 1 V/μm, respectively. No emission was observed for the carbon nanoparticles deposited below 400 °C. The low threshold field of the carbon nanoparticles is attributed to field enhancement effect and the higher degree of graphitization.

High responsivity GaNAsSb p-i-n photodetectors at 1.3µm grown by radio-frequency nitrogen plasma-assisted molecular beam epitaxy

GaNAsSb/GaAs p-i-n photo notdetectors with an intrinsic GaNAsSb photoabsorption layer grown at 350 degrees C, 400 degrees C, 440 degrees C and 480 degrees C, have been prepared using radio-frequency nitrogen plasma-assisted molecular beam epitaxy in conjunction with a valved antimony cracker source. The i-GaNAsSb photoabsorption layer contains 3.3% of nitrogen and 8% of antimony, resulting in DC photo-response up to wavelengths of 1350 nm. The device with i-GaNAsSb layer grown at 350 degrees C exhibits extremely high photoresponsivity of 12A/W at 1.3 microm. These photodetectors show characteristics which strongly suggest the presence of carrier avalanche process at reverse bias less than 5V.

Effect of growth temperature on closely lattice-matched GaAsSbN intrinsic layer for GaAs-based 1.3μm p-i-n photodetector

GaAsSbN layers closely lattice-matched to GaAs were studied for application as the intrinsic layer in GaAs-based 1.3μm p-i-n photodetector. The GaAsSbN was grown as the intrinsic layer for the GaAs∕GaAsSbN∕GaAs photodetector structure using solid-source molecular beam epitaxy in conjunction with a radio frequency plasma-assisted nitrogen source and valved antimony cracker source. The lattice mismatch of the GaAsSbN layer to GaAs was kept below 4000ppm, which is sufficient to maintain coherent growth of ∼0.45μm thick GaAsSbN on the GaAs substrate. The growth temperature of the GaAsSbN layer was varied from 420–480°C. All samples exhibit room temperature photocurrent response in the 1.3μm wavelength region, with dark current density of ∼0.3–0.5mA∕cm2 and responsivity of up to 33mA∕W at 2V reverse bias. Reciprocal space maps reveal traces of point defects and segregation (clustering) of N and Sb, which may have a detrimental effect on the photocurrent responsivity.