Hsby Li

2.7 μm InAs quantum well lasers on InP-based InAlAs metamorphic buffer layers

This work reports 2.7 μm InAs/In0.6Ga0.4As quantum well lasers on InP-based metamorphic InxAl1−xAs graded buffers. X-ray diffraction measurement shows favorable strain compensation effect in the quantum wells. Type-I photoluminescence emission is observed around 2.7 μm at 77 K and red-shifts to 3 μm at 300 K. The continuous-wave lasing wavelength of the laser reaches 2.7 μm at 77 K, which is the longest wavelength from the interband lasing of InP-based antimony-free structures. The threshold current density is as low as 145 A/cm2 and the continuous-wave output power at injection current of 400 mA is over 5 mW.

Tailoring the performances of low operating voltage InAlAs/InGaAs avalanche photodetectors

We present tailoring of the performances of thin multiplication layer InAlAs/InGaAs avalanche photodetectors (APDs) with operating voltages lower than 20 V. Their operating voltages, gain-voltage slopes and dark currents were successfully tailored by changing the electric field distributions in avalanche region. The thin multiplication layer APDs show small activation energies of the dark current ranging from 0.12 to 0.19 eV at temperatures above 220 K, suggesting a band-trap-band tunneling dominant dark current mechanism over this temperature range. The dark currents show very weak temperature dependences at temperatures lower than 175 K, which mainly originate from the band-to-band tunneling and the surface leakage currents. The spectral responsivity of those APDs show anomalous negative temperature coefficients at gain factors larger than 1, which is attributed to the enhanced phonon scattering effect of carriers in the avalanche region at higher temperatures. Good gain factor uniformity at a given bias is observed for those APDs, and the charge layer is found to help improve the gain uniformity.

Nearly lattice-matched short-wave infrared InGaAsBi detectors on InP

This work reports on the demonstration of a short-wave infrared detector nearly lattice matched to InP substrate using quaternary InGaAsBi as the absorption layer. The bismuth content of about 3.2% has red-shifted the 50% cut-off wavelength from about 1.6 μm to 2.1 μm at room temperature, indicating a bandgap reduction of about 180 meV due to bismuth incorporation. The detector shows an encouraging dark current density of 2.4 × 10−4 A/cm2 at bias voltage of −10 mV at 300 K. This work shows the promising potential of InP-based lattice-matched InGaAsBi detectors for short-wave infrared detection.

Evaluation of the performance correlated defects of metamorphic InGaAs photodetector structures through plane-view EBIC

To evaluate the performance correlated imperfection or defect features of metamorphic InGaAs photodetector structures, a scanning electron microscopy scheme including both plane-view electron beam induced current (EBIC) and secondary electron (SE) images have been used. The abilities, merits and limitations as well as some case-dependent properties of EBIC have been discussed in detail. The devices of similar structures grown on InP or GaAs substrates with quite different lattice mismatch show discriminated defect distribution patterns, prompting their distinct origins, which have been confirmed by cross-sectional transmission electron microscopy observation. Using self-developed image processing software the EBIC features of the samples are statistically analyzed, which validated the qualitative correlation between the EBIC data and device dark current. Fusing of EBIC and SE images has also been attempted to enhance the defect visibility. Results indicate that EBIC is feasible to investigate the effects of defects on the device performance not only in research work, but also for product quality monitor purposes.

InP-based Sb-free Lasers and Photodetectors in 2-3 μm Band

Zhang et al. efforts on the explore of InP-based Sb-free 2-3 μm band lasers and photodetectors are introduced, including the 2-2.5 μm band type I InGaAs MQW lasers under pseudomorphic triangle well scheme, 2.5-3.0 μm band type I InAs MQW lasers under metamorphic strain compensated well scheme, as well as InGaAs photodetectors of high indium contents with cut-off wavelength large than 1.7 μm. All device structures are grown using gas source MBE method, and CW operation above room temperature have been reached for the lasers with wavelength less than 2.5 μm. Pulse operation of 2.9 μm lasers at TE temperature also have been reached The dark current of 2.6 μm InGaAs photodetectors have been decreased notably with the inserting of supperlattice electron barriers, those types of epitaxial materials have been used to the development of FPA modules for space remote sensing applications.

High-performance InP-based InAs triangular quantum well lasers operating beyond 2 μm

InP-based antimony-free In0.53Ga0.47As/InAs/In0.53Ga0.47As strained triangular quantum well lasers have been demonstrated for the light sources with wavelength beyond 2 μm. Theoretical estimation shows that the triangular quantum well owns the longer emission wavelength than the rectangular quantum well with the same strain extent. The triangular quantum well was formed experimentally by using gas source molecular beam epitaxy grown digital alloy, and the growth temperature of the triangular quantum wells was optimized. The triangular quantum well lasers with emission beyond 2.2 μm under continuous-wave operation at temperatures higher than 330 K have been demonstrated. The performances of the triangular quantum well lasers are improved comparing to those of InAs rectangular quantum lasers with the nearly same lasing wavelength.