Microwave performance of ZnO/ZnMgO heterostructure field effect transistors

Abstract

We report the first microwave performance of single crystalline ZnO/ZnMgO heterostructure field‐effect transistors (HFETs). The structure consisted of a 15‐nm‐thick ZnO channel layer was grown by molecular beam epitaxy (MBE) on an a‐sapphire substrate. Two‐finger type HFETs with 1 or 2‐µm‐long gate were fabricated and measured for microwave performance. The transconductance of the HFETs are 28 and 23 mS/mm for 1 and 2‐µm‐gate devices, respectively. The microwave measurement of ZnO‐based TFTs revealed that the current gain cutoff frequency fT of 1.75 GHz and that of unilateral power gain fmax of 2.45 GHz for 1‐µm‐gate HFET. Electron velocity obtained by two‐terminal measurements implies that the structural design is crucial for further improvement of the high‐frequency performance of ZnO/ZnMgO HFETs. Small‐signal microwave characteristics of a 1‐µm‐gate ZnO/ZnMgO heterostructure FET. The current gain cutoff frequency of 1.75 GHz and the unilateral power gain cutoff frequency of 2.45 GHz were obtained.

Impact of Mg content on native point defects in MgxZn1−xO (0 ≤ x ≤ 0.56)

“…C ZnO is a prime candidate for next generation opto-and microelectronics with a large exciton binding energy that permits efficient light emission at room temperature. [1][2][3] The 3.37 eV band gap of ZnO can be tuned by incorporating either Mg or Cd 4 to enable complex heterostructures that can enhance transport properties in ZnO based transistors 5,6 and optoelectronic efficiency of UV lasers, 7 light emitting diodes, and solar blind detectors. 8 The ZnO band gap increases with Mg alloying and Mg can be incorporated into ZnO at low concentrations without significantly disrupting the wurtzite structure.…”

Demonstration of radio-frequency response of amorphous IGZO thin film transistors on the glass substrate

“…The transfer curve suggests a subthreshold slope (SS), a saturation mobility (l sat ), a maximum transconductance (g m ), a current on-off ratio, and a threshold voltage (V th ) of 0.29 V/decade, 12.7 cm 2 /V s, 6.3 mS/mm, 1.4 Â 10 6 , 0.27 V, respectively. Typically a higher g m is obtained for a depletion mode device due to its higher carrier density [8][9][10][11]. However, enhancement mode operation is more desired for many applications due to less power consumption.…”

“…In addition, our device exhibits a f max /f T ratio as high as 2.8, which is mainly attributed to the high drain current and the low drain output conductance [21]. To evaluate the high-speed capability of a-IGZO, saturation velocity (v s ) was estimated following the relationship f T = v s /2pL G [10]. A saturation velocity v s of 3.8 Â 10 5 cm/s is obtained.…”

“…Recently, the RF performance of metal oxide based transistors was explored using small gate length devices [8][9][10][11][12][13][14]. Nanocrystalline ZnO TFTs fabricated by pulsed laser deposition (PLD) at 400°C on GaAs or high resistivity Si substrates have demonstrated mobility over 100 cm 2 /V s, current density >400 mA/mm, and high frequency response (current gain cutoff frequency f T = 2.45 GHz, maximum frequency of oscillation f max = 7.45 GHz) [8,9].…”

Monte Carlo analysis of transient electron transport in wurtzite Zn1−xMgxO combined with first principles calculations

“…[11][12][13][14] Particularly, the application to high frequency devices has attracted significant attentions these years. 15 For high frequency working applications, detailed investigations on the electron transport properties in Zn 1−x Mg x O are required, especially on the transient electron transport characteristics. Up to date, only limited studies have been reported on the steady-state electron transport properties of Zn 1−x Mg x O.…”