Manufacturable AlSb/InAs HEMT Technology for Ultra-Low Power Millimeter-Wave Integrated Circuits

High electron mobility transistors with InAs channels and sub 0.1m metal gates, have demonstrated a 100% improvement in low-power, high-speed figure of merits over conventional InAlAs/InGaAs lattice-matched HEMTs and MHEMTs. AlSb/InAs MHEMTs exhibit transconductances as high as 1.3 S/mm at drain biases as low as 0.3 V, while maintaining fT and fmax results greater than 220 GHz and 270 GHz, respectively. In this paper, we will discuss our efforts to develop this technology for revolutionary low-power, high frequency MMIC applications. INTRODUCTION Monolithic Millimeter-wave Integrated Circuits (MMIC) based upon InAs-channel HEMT’s have the potential to enable revolutionary low-noise, low-power, and high-speed applications. As shown in Table 1, InAs electronic properties, such as electron mobility and peak velocity, are nearly two times larger as compared to state-of-the-art InXGa1-XAs-channels. InAlAs/InGaAs HEMT’s grown on lattice-matched InP substrate offer the best combination of low-power and lownoise MMIC’s to date [1-2]. Based on our device data, as shown in Figure 1, we estimate InAs-based HEMT performance meets or exceeds InAlAs/InGaAs HEMT but with only one-tenth the power dissipation. However, development of InAs channel devices is challenging because of the lack of viable semi-insulating substrates for lattice-matched growth. Metamorphic growth using the AlXGa1-XSbYAs1-Y/InAs material system, which has a lattice constant near 6.1 Å, as shown in Figure 2, has proven to be a viable alternative for state-of-the-art InAschannel HEMTs [3-5] and researchers in this field now routinely achieve electron mobility > 15,000 cm/V-s with tensile strained InAs channels. However, the approach does hold several unique challenges such as intrinsic material stability, gate leakage, and yield limiting defect densities, which have been incrementally addressed over the years [6]. Only recently have the first AlSb/InAs MHEMT based MMIC’s been demonstrated [7,8]. In this paper, we will discuss the successful development of a manufacturable AlSb/InAs MHEMT technology at Northrop Grumman Space Technology (NGST) and Naval Research Laboratory (NRL) for ultra low-power, high frequency MMIC products. 0 100 200 300 400 500 600 0 0.25 0.5 0.75 1 Drain-Source Voltage (V) D ra in C u rr en t ( m A /m m ) InAlAs/InGaAs HEMT & MHEMT: 75 mW/mm AlSb/InAs HEMT: 6 mW/mm Fig. 1 AlSb/InAs HEMT (solid) bias points for minimum noise figure and lowest DC power dissipation, compared to InAlAs/InGaAs HEMT (dashed). Curves displayed for gate voltage step of 0.1 V. Table 1. HEMT Channel Electron Transport Properties Property InAs In0.53Ga0.47As GaAs me* 0.023 0.041 0.067 μ (cm/V-sec) 20000 8000 4500 Peak velocity (10 cm/sec) 4.0 2.7 2.2 Γ-L valley seperation (eV) 0.9 0.55 0.31 Band Gap (eV) 0.36 0.72 1.42 Gate Voltage Steps of 0.1 V E ne rg y G ap ( eV ) W av el en gt h (μ m ) Lattice Constant (Å) Ge Si GaAs GaP