Unstrained Ga1–xInxSb quantum well (QW) channel using strained‐Al0.40In0.60Sb/Al1–yInySb stepped buffer layer grown on GaAs (100) substrate is investigated. Ga1–xInxSb QW is lattice‐matched to the Al1–yInySb lower buffer layer. Sheet electron density (Ns) of Ga1–xInxSb QW is about twice that of InSb one. Electron mobility (μ) increases with increasing In content x of Ga1–xInxSb. Unstrained Ga0.22In0.78Sb QW channel using strained‐Al0.40In0.60Sb/Al0.25In0.75Sb stepped buffer has Ns of 2.05 × 1012 cm−2 and μ of 15 500 cm2 V−1 s−1. Compared with the InSb QW channel, Ns increases by a factor of 193% and μ decreases to 87%. Consequently, the sheet resistance decreases to 59%. These results indicate that the unstrained Ga1–xInxSb QW channel using strained‐Al0.40In0.60Sb/Al1–yInySb stepped buffer is effective to improve the electron transport properties.

GaInSb is one of the attractive Sb‐based channel materials for high electron mobility transistors (HEMTs) that can operate in the terahertz band. The effect of strain in the channel on the electron transport properties of Ga1−x In x Sb channel HEMT structures (x = 0.60, 0.78, 0.85, 0.90, and 0.94) with the strained‐Al0.40In0.60Sb/Al0.25In0.75Sb stepped buffer is investigated. The strain in the Ga1−x In x Sb channel layer is determined by the lattice constant of Al0.25In0.75Sb lower buffer layer. The electron mobility (μ) shows the maximum value of 15 100 cm2 V−1 s−1 at x = 0.78 (unstrained), which has the minimum threading dislocation density (TDD). The value for sheet electron density (N s) increases with decreasing x, and saturates at about 2.1 × 1012 cm−2 when unstrained or tensile strained. The minimum sheet resistance (R s) is 202 Ω/□ for the unstrained Ga0.22In0.78Sb channel.

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Unstrained Ga1–xInxSb quantum well (QW) channel using strained‐Al0.40In0.60Sb/Al1–yInySb stepped buffer layer grown on GaAs (100) substrate is investigated. Ga1–xInxSb QW is lattice‐matched to the Al1–yInySb lower buffer layer. Sheet electron density (Ns) of Ga1–xInxSb QW is about twice that of InSb one. Electron mobility (μ) increases with increasing In content x of Ga1–xInxSb. Unstrained Ga0.22In0.78Sb QW channel using strained‐Al0.40In0.60Sb/Al0.25In0.75Sb stepped buffer has Ns of 2.05 × 1012 cm−2 and μ of 15 500 cm2 V−1 s−1. Compared with the InSb QW channel, Ns increases by a factor of 193% and μ decreases to 87%. Consequently, the sheet resistance decreases to 59%. These results indicate that the unstrained Ga1–xInxSb QW channel using strained‐Al0.40In0.60Sb/Al1–yInySb stepped buffer is effective to improve the electron transport properties.