Demonstration of a quick process to achieve buried heterostructure QCL leading to high power and wall plug efficiency

Abstract

Together with the optimal basic design, buried heterostructure quantum cascade laser (BH-QCL) with semi-insulating regrowth offers unique possibility to achieve an effective thermal dissipation and lateral single mode. We demonstrate here for the first time realization of BH-QCLs with a single step regrowth of highly resistive (>1x10 8 ohm·cm) semiinsulating InP:Fe in less than 45 minutes in a flexible hydride vapour phase epitaxy process for burying ridges etched down to 10-15 µm deep both with and without mask overhang. The fabricated BH-QCLs emitting at ~4.7 µm and ~5.5 µm were characterized. 2 mm long 5.5 µm lasers with ridge width 17-22 µm, regrown with mask overhang, exhibited no leakage current. Large width and high doping in the structure did not permit high current density for CW operation. 5 mm long 4.7 µm BH-QCLs of ridge widths varying from 6-14 µm regrown without mask overhang, besides being spatially monomode, TM 00 , exhibited WPE of ~8-9% with an output power of 1.5 -2.5 W at room temperature and under CW operation. Thus, we demonstrate a simple, flexible, quick, stable and single-step regrowth process with extremely good planarization for realizing buried QCLs leading to monomode, high power and high WPE.

Room temperature operation of a deep etched buried heterostructure photonic crystal quantum cascade laser

“…[28] The space between the etched pillars was filled with semi-insulating Fe-doped InP using a low pressure Hydride vapour phase epitaxy (HVPE). [28][29][30] A Si doped InP top cladding was regrown using Metal Organic Vapour Phase Epitaxy (MOVPE). [28] The top electrodes were formed using e-beam evaporated Ti/Pt/Au layers (10nm/40nm/250nm) in a lift off process.…”

High-Power Mid-Infrared (λ∼3-6 μm) Quantum Cascade Lasers

“…Even for devices which exhibit low M 2 values, beam instabilities may be present making them unsuitable for applications requiring high pointing accuracy. Studies on narrow-ridge-width BH QCLs indicate that the beam properties and mode stability can be highly sensitive, under QCW/CW operating conditions, to the dimensions of the width of the buried ridge as well as the BH-regrowth morphology [100]. Accurate control of the ridge width and Fe:InP regrowth planarization is facilitated by employing ICP dry etching and hydride vapor phase epitaxy (HVPE), as shown in Fig.…”

“…20. The high growth rates afforded by HVPE [51,100] are attractive, since the Fe:InP regrowth necessary is generally very thick (10-15 m) when forming the BH. While MOCVD regrowth of the Fe:InP is also possible, it is generally more challenging to achieve highly planar surface morphology for the selective growth process [101].…”