High peak-power, room-temperature operation is reported for ridge waveguide quantum cascade lasers (QCLs) monolithically integrated onto a silicon substrate. The 55-stage laser structure with an AlInAs/InGaAs core and InP cladding was grown by molecular beam epitaxy directly onto an 8-inch diameter germanium-coated silicon substrate template via a III–V alloy metamorphic buffer. Atomic force microscope imaging demonstrated a good quality surface for the full QCL structure grown on silicon. Fabricated 3mm by 26µm lasers operate at room temperature, deliver more than 3W of peak optical power, and show approximately 3% wall plug efficiency and 4.3 kA/cm2 threshold current density with emission wavelength centered at 11.5µm. The lasers had a high yield with only around 15% max power deviation and no signs of performance degradation were observed over a 10h burn in period at maximum power. Singled-lobed high quality output beam was measured for 3mm by 22 µm devices. Correlation between laser performance and defect density in the laser core for several QCL structures grown on lattice-mismatched substrates will also be discussed in this talk.
MBE and MOVPE growths of InP-based extended wavelength and GaSb-based IR emitter and detector structures have progressed to production mode. These photonics device structures are typically grown using large format, multi wafer MBE and MOCVD tools and on large diameter substrates (100 to 150 mm). In this work, material characterization data of advanced InP- and GaSb based epitaxial structures will be shown. Multi point measurements showing cross-wafer and cross-platen uniformity will also be shared. Finally, detailed analysis of run-to-run epiwafer data will be presented to demonstrate the manufacturability of our production epitaxial process for these advanced photonics device structures.
GaSb-based infrared (IR) photodetector technology progression is toward larger-format focal plane arrays (FPAs). This requires a performance-based and cost-based manufacturing process on larger diameter substrates for improved throughput, volume, and yield. IQE has demonstrated molecular beam epitaxy (MBE) growth processes for barrier-design detectors (nBn) in multi-wafer configurations on 4-inch and 5-inch diameter GaSb substrates, and via a metamorphic process on 4-inch and 6-inch GaAs substrates. Recently we took the next step in this progression, growing nBn detectors on 6-inch Si substrates coated with CVD-grown Ge, opening the door for potential integration with Si-based electronic circuitry. Here, we compare the epiwafer characteristics (morphology, x-ray, PL) and diode performance (turn-on, QE, cutoff wavelength) of this M-nBn on Ge-Si with the same M-nBn on GaAs and the corresponding nBn structure grown on native GaSb substrate. Similar performance was obtained on all three types of substrates. We also present FPA data based on a 640×512 pixel, 15 μm pitch process without substrate removal, where QE ~ 80%, NE▵T < 20 mK, and operability <99% was demonstrated. The results represent an important technological path toward next-generation large-format IR detector array applications.
We report the experimental results of a 40-stage InP-based quantum cascade laser (QCL) structure grown on a 6-inch GaAs substrate with metamorphic buffer (M-buffer). The laser structure’s strain-balanced active region was composed of Al0.78In0.22As/In0.73Ga0.27As and an all-InP, 8 μm-thick waveguide. The wafer was processed into ridge-waveguide chips (3mm x 30 μm devices) with lateral current injection scheme. Devices with high reflection coating delivered power in excess of 200 mW of total peak power at 78K, with lasing observed up to 230K. Preliminary reliability testing at maximum power showed no sign of performance degradation after 200 minutes of runtime. Measured characteristic temperatures of T0 ≈ 460 K and T1 ≈ 210 K describes the temperature dependence for threshold current and slope efficiency, respectively, in the range from 78K to 230K. Partial high reflection coating was used on the front facet to extend the lasing range up to 303K.
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