ISSN 1063-7850, Technical Physics Letters, 2011, Vol. 37, No. 10, pp. 935–938. © Pleiades Publishing, Ltd., 2011. Original Russian Text © D.A. Starostenko, V.V. Sherstnev, P.A. Alekseev, I.A. Andreev, N.D. Il’inskaya, G.G. Konovalov, O.Yu. Serebrennikova, Yu.P. Yakovlev, 2011, published in Pis’ma v Zhurnal Tekhnicheskoi Fiziki, 2011, Vol. 37, No. 19, pp. 95–103. 935 Photodiodes operating in the middle IR range (2– 5 μm) can be used in solving various tasks of ecological monitoring, gas analysis, detection of combustion and explosion products, analysis of food products and bio- logical objects, temperature sensors and special-pur- pose tracing systems, and medical applications [1–3]. In view of the extensive development of industry, the task of ecological monitoring becomes a very impor- tant direction of environment protection. The solu- tion of this task involves various problems of the spec- tral analysis of atmosphere in the wavelength range of 2–5 μm, which contains numerous absorption bands of water, industrial gases, and other substances, including those harmful for the human organism. For example, the middle IR range contains the absorption lines of gases such as ethylene, methane, acetylene, sulfuric anhydride, carbon mono- and dioxide, etc. [4]. The problems of medical diagnostics (in particu- lar, expiration gas control) also require the develop- ment of sensors for CO 2 (4.25 μm) and CO (4.7 μm). Recently, we described [5] photodiodes based on InAs/InAs 0.88 Sb 0.12 /InAsSbP/InAs heterostructures operating at room temperature in a middle-IR interval of 3.5–4.9 μm wavelength range. These heterostruc- tures with a photosensitive area diameter of 0.3 mm were grown by liquid phase epitaxy (LPE) on InAs substrates. The photodiodes exhibited a monochro- matic responsivity of 0.6–0.8 A/W at λ max = 4.2– 4.7 μm and has a dark current density of (1.5–7.5) × 10 –1 A/cm 2 at a reverse bias of 0.2 V. The differential resistance at zero bias reaches up to 700–800 Ω. The detection ability of photodiodes in the spectral interval of maximum sensitivity reaches (5–8) × 10 8 cm Hz 1/2 W –1 . However, these photodiodes possessed a rather narrow spectral sensitivity range (3.5–4.8 μm) with a half- width of 0.8–0.9 μm, which does not meet require- ments of many applications. The narrow spectral sen- sitivity range was related to the presence of a thin (1 μm) subcontact layer of InAs. Zakhgeim et al. [6] used an InAs/InAs 0.92 Sb 0.08 /InASbP heterostructure in the flip-chip photodetector design with illumina- tion via the InAs substrate. Photodiodes with the InAsSb active region and the illumination via degener- ate substrate had a spectral sensitivity range of 2.6 4.6 μm with a maximum sensitivity at 3.8– 4.0 μm. The high monochromatic responsivity of these photodiodes allowed their detection ability to reach 2.8 × 10 9 cm Hz 1/2 W –1 at a wavelength of 4.3 μm. A long-wavelength photodetector based on an InAs/InAsSb/InAs heterostructure with flip-chip design and illumination via the InAs substrate [7] had a maximum spectral sensitivity at 4.55 μm and a long- wavelength cutoff at 5.1 μm. The aforementioned photodiodes had a current responsivity within 0.4– 0.6 A/W and a differential resistance at zero bias on a level of 10–15 Ω. The detection ability of photodiodes at 4.55 μm reached 5 × 10 9 cm Hz 1/2 W –1 . It should be noted that these results were determined to a consider- Room-Temperature Photodiodes Based on InAs/InAs 0.88 Sb 0.12 /InAsSbP Heterostructures for Extended (1.5–4.8 μm) Spectral Range D. A. Starostenko, V. V. Sherstnev, P. A. Alekseev, I. A. Andreev*, N. D. Il’inskaya, G. G. Konovalov, O. Yu. Serebrennikova, and Yu. P. Yakovlev Ioffe Physical Technical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia St. Petersburg State Electrotechnical University, St. Petersburg, 197376 Russia *e-mail: igor@iropt9.ioffe.ru Received May 10, 2011 Abstract—Photodiodes with a photosensitive area of 0.45 × 0.45 mm 2 operating at room temperature in a wavelength range bounded by 4.9 μm have been created on the basis of InAs/InAs 0.94 Sb 0.06 /InAsSbP/InAs 0.88 Sb 0.12 /InAsSbP/InAs heterostructures grown by liquid phase epitaxy. A distinguishing feature of the proposed photodiodes is extended (λ max = 1.5–4.8 μm) spectral sensitivity range, in which the photodiode is characterized by a monochromatic responsivity of 0.5–0.8 A/W and a dark current density of 1.0–1.5 A/cm 2 at a reverse bias of 0.2 V. The differential resistance at zero bias reaches up to 20–100 Ω. The detection ability of photodiodes in the region of maximum sensitivity reaches (1–2) × 10 8 cm Hz 1/2 W –1 . DOI: 10.1134/S1063785011100142