Optimum growth window for InAs/GaInSb superlattice materials tailored for very long wavelength infrared detection
The authors report growth studies to develop an InAs/GaInSb superlattice (SL) material for very long wavelength infrared detection. They select a SL structure of 47.0 Å InAs/21.5 Å Ga0.75In0.25Sb that is designed for the greatest possible detectivity, and tune growth conditions to achieve the best quality ternary material. Since the material quality of grown layers is particularly sensitive to extrinsic defects such as nonradiative recombination centers generated during the growth process, the authors investigate the effect of the growth temperature (Tg) on the spectral photoresponse (PR) and carrier recombination lifetime using photoconductivity and time-resolved differential reflectivity measurements. Results indicate that a molecular beam epitaxy growth process the authors developed produces a consistent energy gap around 50 meV, determined from the PR spectra, but the intensity of the spectra is sensitive to Tg. For SLs grown at Tg between 390 and 470 °C, the PR signal intensity gradually increases as Tg increases from 400 to 440 °C, reaching a maximum at 440 °C. Outside this growth window, the SL quality deteriorates very rapidly. However, the carrier recombination lifetime measured at 300 K was not sensitive to Tg. Although the SL sample grown at 430 °C produced the longest lifetime of 84 ns, the average 300 K lifetime value remained around 74 ns.