High Performance InAlAs/InAs/InGaAs Pseudomorphic High Electron Mobility Transistors

Abstract

High electron mobility transistors (HEMTs) with a pseudomorphically strained InAs channel (InAs-PHEMTs) were fabricated, and their high frequency characteristics were estimated by measuring the S-parameters. For a VDS of 1.4 V and VGS of 0.3 V, InAs-PHEMTs showed an excellent intrinsic cut-off frequency (fT, int.) as high as 90 GHz regardless of their longer LG (0.7 μm). Since fT is known to be inversely proportional to LG to the first approximation, fT, int. of our InAs-PHEMTs may reach 630 GHz if their LG is reduced to 0.1 μm.Moreover, we calculated the InAs-PHEMTs' energy state and potential profile by self-consistently solving the Schrödinger and Poisson equations. In solving the Schrödinger equation, the energy-dependent effective mass was employed to take into account the strong non-parabolicity of InAs conduction-band based on the k·p perturbation theory by E. O. Kane. It was clarified that most electrons are confined to the InAs layer. On the contrary, if the non-parabolicity is not taken into account, electrons will spread over the InGaAs channel layer.

Ultrafast Optical Response of InAlAs/InAs/InGaAs Pseudomorphic High Electron Mobility Transistors

“…Hot holes are known to penetrate into the gate region over the valence band discontinuity, ÁE v , thereby deteriorating the HEMT characteristics. 10) However, this effect is considered to be small for P-HEMTs for the following reasons: (1) the ÁE v between the InAlAs and InAs layers is as large as 0.31 eV 6) as compared with that between the InAlAs and InGaAs layers and (2) the hole transit time 1 obtained from the optical response is independent of V DS at a higher V DS (Fig. 5).…”

“…10) 2DEG concentration of the pseudomorphic channel in InAs-PHEMTs. 6) Clearly, the Auger mechanism dominates the recombination in InAs. Using the experimentally obtained CHSH (4:0 Â 10 À11 s), it was found that holes accumulated in the source region, and that their concentration reached as high as 2 Â 10 18 cm À3 .…”

“…5) Recently, we have pointed out that the non parabolicity of the conduction band must be strictly taken into account when discussing the characteristics of HEMTs with the InAs channel. 6) In addition, we have demonstrated that InAs-PHEMT can operate as not only a high-speed transistor but also an ultra high-speed optical receiver. 7) In this work, we show the dependence of optical response on drain-to-source voltage (V DS ) for InAs-PHEMTs and clarify the physical mechanism for the response time.…”

Characteristics of PHEMTs and MSM photodetectors simultaneously fabricated on same epitaxial wafer with In0.75Ga0.25As/InGaAs channel layer

“…In our previous study regarding the effect of optical irradiation on InAlAs/InGaAs HEMT characteristics, we demonstrated that a shift of threshold voltage (V TH ) in InAlAs/InGaAs HEMTs is caused by the change in the Fermi level due to the holes accumulated in the source region [3,4]. The carrier lifetime of accumulated holes is dominated by Auger recombination of holes in the two-dimensional electron gas (2DEG) [3][4][5]. Furthermore, we have shown that InAlAs/InGaAs HEMTs have a high responsivity when they are used as optical receivers [5].…”

“…The carrier lifetime of accumulated holes is dominated by Auger recombination of holes in the two-dimensional electron gas (2DEG) [3][4][5]. Furthermore, we have shown that InAlAs/InGaAs HEMTs have a high responsivity when they are used as optical receivers [5]. Recently, we have demonstrated that InAs-PHEMTs can operate as not only high-speed transistors but as ultra-high speed optical receivers [3][4][5][6].…”