Flexible indium–gallium–zinc–oxide Schottky diode operating beyond 2.45 GHz

Abstract

Mechanically flexible mobile phones have been long anticipated due to the rapid development of thin-film electronics in the last couple of decades. However, to date, no such phone has been developed, largely due to a lack of flexible electronic components that are fast enough for the required wireless communications, in particular the speed-demanding front-end rectifiers. Here Schottky diodes based on amorphous indium-gallium-zinc-oxide (IGZO) are fabricated on flexible plastic substrates. Using suitable radio-frequency mesa structures, a range of IGZO thicknesses and diode sizes have been studied. The results have revealed an unexpected dependence of the diode speed on the IGZO thickness. The findings enable the best optimized flexible diodes to reach 6.3 GHz at zero bias, which is beyond the critical benchmark speed of 2.45 GHz to satisfy the principal frequency bands of smart phones such as those for cellular communication, Bluetooth, Wi-Fi and global satellite positioning.

Geometry-Based Tunability Enhancement of Flexible Thin-Film Varactors

“…The upper dashed line shows the calculation in accumulation C calc,acc , assuming that the whole a-IGZO island becomes conductive and the effective t decreases to the thickness of the Al 2 O 3 layer. The calculations are in agreement with the measurements showing deviations smaller than 4 % using ǫ r,IGZO = 16 [18] and ǫ r,Al 2 O 3 = 7 [19]. The schematic device cross section in Fig.…”

Complementary Integrated Circuits Based on p-Type SnO and n-Type IGZO Thin-Film Transistors

“…For instance, IGZO thin-film transistors (TFTs) have started to replace amorphous silicon TFTs for backplane drivers of flat-panel displays [1]. Flexible IGZO Schottky diodes operating beyond 2.45 GHz have already satisfied the principal frequency of smart phones [5]. Subthreshold Schottky-barrier IGZO TFTs have been demonstrated to be useful for sensor interface circuits in wearable electronics [6].…”

Effects of substrate and anode metal annealing on InGaZnO Schottky diodes

“…The discrepancy between N depl and N e is mainly attributed to the subgap traps in amorphous semiconductor. 11,14,16 Sample A has the lowest ratio N depl /N e of 4.0 × 10 2 , which means for each free electron, there are roughly 4.0 × 10 2 ionized atoms. This indicates that among the four samples, sample A has the lowest subgap trap density.…”

“…The limited studies on IGZO Schottky diodes have been focused on achieving large barrier heights,  B , 9,10 high rectification ratios, I on/off , 9,11,12 low ideality factors, n, 9,10,13 and high-frequency operation. 11,12,14 So far, thermal annealing at ~200 ˚C has been used in most studies. The best annealed diodes fabricated by using the sputtering technique showed an I on/off of ~10 8 ,  B of ~0.9 eV, and n of ~1.2.…”