Comparison of semi-insulating InAlAs and InP:Fe for InP-based buried-heterostructure QCLs

• Published in: Journal of crystal growth Vol. 425; pp. 360 - 363
• Main Authors: Flores, Y.V., Aleksandrova, A., Elagin, M., Kischkat, J., Kurlov, S.S., Monastyrskyi, G., Hellemann, J., Golovynskyi, S.L., Dacenko, O.I., Kondratenko, S.V., Tarasov, G.G., Semtsiv, M.P., Masselink, W.T.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2015
• Subjects: A3. Molecular beam epitaxy; B2. Semiconducting III–V materials; B3. Heterojunction semiconductor devices; B3. Infrared devices; Cladding; Devices; Electrical resistivity; Insulation; Lasers; Morphology; Spacers; Thin films; B3. Heterojunction semiconductor devices; A3. Molecular beam epitaxy; B2. Semiconducting III–V materials; B3. Infrared devices
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2015.03.016

In a previous work [Flores et al., J. Cryst. Growth 398 (2014) 40] [3] we demonstrated the advantages of using a thin InAlAs spacer layer in the fabrication of buried-heterostructure quantum-cascade lasers (QCLs), as it improves the morphology of the interface between the laser core and the InP:Fe lateral cladding. In this paper we investigate aspects of InAlAs, which are relevant for its role as insulating lateral cladding of the laser sidewalls: carrier traps, electrical resistivity, and functionality as a sole lateral cladding. We find that a thin InAlAs spacer layer not only improves the regrowth interface morphology, but also eliminates interface-related shallow electronic states, thus improving the electrical resistivity of the interface. We further find that bulk InAlAs grown by gas-source molecular-beam epitaxy as well as InP:Fe are semi-insulating at room temperature, with specific resistivities of 3×107Ωcm and 2×108Ωcm, respectively. Both materials have also a high thermal activation energy for electrical conductivity (0.79eV and 0.68eV, respectively). In order to compare the performance of InP:Fe and InAlAs as a lateral cladding, lasers were fabricated from the same QCL wafer with differing stripe insulation materials. The resulting lasers differ mainly by the lateral insulation material: SiO2, InP:Fe (with InAlAs spacer), and pure InAlAs. All devices show a similar performance and similar temperature dependence, indicating insulating properties of InAlAs adequate for application in lateral regrowth of buried-heterostructure QCLs.
•A thin InAlAs spacer layer eliminates interface-related shallow electronic states.•Bulk InAlAs grown by gas-source MBE is semi-insulating at room temperature.•Bulk InP:Fe grown by gas-source MBE is semi-insulating at room temperature.•InAlAs and InP:Fe have high activation energies (0.79eV and 0.68eV, respectively).