Comprehensive modeling of the extrinsic transconductance for InxGa1-xAs/In0.52Al0.48As quantum-well high-electron-mobility transistors

초록

This paper presents the comprehensive modeling of extrinsic transconductance (g<inf>m_ext</inf>) in the saturation regime for In<inf>x</inf>Ga<inf>1-x</inf>As/In<inf>0.52</inf>Al<inf>0.48</inf>As quantum-well (QW) high-electron-mobility transistors (HEMTs) with L<inf>g</inf> from 10 μm to sub-100 nm, covering the ballistic and mobility relevant regimes. First, we fabricated and characterized two types of lattice matched (LM) channel In<inf>0.53</inf>Ga<inf>0.47</inf>As QW HEMTs on a 3-inch InP substrate. One of these was fully fabricated with an i-line stepper, yielding L<inf>g</inf> from 10 μm to 0.5 μm, and the other was fabricated in a mix & match manner with a combination of an i-line stepper and an e-beam lithography equipment, where T-shaped gates were implemented using a tri-layer resist stack of ZEP520A-PMGI-ZEP520A in the e-beam lithography process. Using devices with a wide range of L<inf>g</inf> values, we examined the transconductance (g<inf>m</inf>) characteristics in saturation and attempted to correlate them to analytical expressions capable of describing the carrier transport properties of the devices using only physical parameters, such as the gate capacitance (C<inf>gi</inf>) apparent mobility (μ<inf>n_app</inf>), and saturation velocity (v<inf>sat</inf>), and the series resistances (R<inf>s</inf> and R<inf>d</inf>). In this way, we assessed the dependences of the extrinsic transconductances of the fabricated devices on their gate lengths, with the model parameters of C<inf>gi</inf> = 0.65 μF/cm2, μ<inf>n_app</inf> = 9400 cm2/V⋅s, v<inf>sat</inf> = 4.3 × 107 cm/s and R<inf>s</inf> = 147 Ω⋅μm. These values were observed to be well-matched with those of the physical parameters. Most importantly, we extended the proposed approach to realistically project the increase in g<inf>m_ext</inf> that could be accomplished by improving certain device parameters. © 2022 Elsevier Ltd

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