Improved Electron Transport Properties of Ga_1–xIn_xSb Quantum Well Channel Using Strained‐Al_0.40In_0.60Sb/Al_1–yIn_ySb Stepped Buffer

Abstract

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.

Effect of Strain in Channel on Electron Transport Properties of Ga1−xInxSb High Electron Mobility Transistor Structures with Strained‐Al0.40In0.60Sb/Al0.25In0.75Sb Stepped Buffer

“…The μ value increases with increasing In content and reaches the maximum value of 15 500 cm 2 V −1 s −1 when x = 0.78 and y = 0.75 within the conditions of epi‐structure in ref. [7]. In contrast, the N s value is almost constant.…”

“…Figure 1 shows the strain in the Ga 1Àx In x Sb channel when the In content x of the Ga 1Àx In x Sb channel and/or the In content y of the Al 1Ày In y Sb lower buffer are varied. In our previous work, [7] we varied the x and y values under the conditions of an unstrained channel (ε || ¼ 0), which are shown by blue closed circles in Figure 1. ε || is defined by ε || ¼ (a e Àa s )/a s , [8,9] where a e is a lattice constant of Ga 1Àx In x Sb channel and a s is a lattice constant of Al 1Ày In y Sb lower buffer.…”

“…The μ value increases with increasing In content and reaches the maximum value of 15 500 cm 2 V À1 s À1 when x ¼ 0.78 and y ¼ 0.75 within the conditions of epi-structure in ref. [7]. In contrast, the N s DOI: 10.1002/pssa.202200529 GaInSb is one of the attractive Sb-based channel materials for high electron mobility transistors (HEMTs) that can operate in the terahertz band.…”

“…To increase N s while keeping relatively high μ , we devised and grew Ga 1− x In x Sb HEMT structures with strained‐Al 0.40 In 0.60 Sb/Al 1− y In y Sb stepped buffer. [ 7 ] These HEMT structures make it possible to deepen the QW channel while leaving GaInSb unstrained. Figure shows the strain in the Ga 1− x In x Sb channel when the In content x of the Ga 1− x In x Sb channel and/or the In content y of the Al 1− y In y Sb lower buffer are varied.…”