Field-Effect Transistors with Submicrometer Gate Lengths Fabricated from LAO-STO-Based Heterostructures

 

Due to their wide spectrum of functionalities, complex oxides are highly interesting for use in electronic devices. We have fabricated and analyzed very small field effect transistors (FETs) built from complex oxides and explored the possible existence of short-channel effects. For this we studied devices with various gate lengths fabricated from LaAlO3-SrTiO3 heterostructures.

Using a highest-standard epitaxial deposition system and state-of-the-art electron beam lithography, we succeeded in fabricating FETs with gate lengths as small as 60 nm. Short-channel effects comparable to those known from semiconductors were observed for devices with gate lengths smaller than 1 µm. Due to the fundamentally different operation principles, theoretical methods for describing semiconductor physics are applicable only with considerable restrictions. This work paves the way for further experimental investigation of complex-oxide devices with critical feature sizes of a few 10 nm and encourages theoretical work for a better understanding of these systems.

This work has been published in

Phys. Rev. Applied 4, 064003 (2015)

(arXiv:1511.07680 [cond-mat.mes-hall])

 

 

<p><strong>Figure 1</strong></p>
<div>(a) Photograph of a 10 x 10 mm<sup>2 </sup>sized sample patterned by electron-beam lithography. It comprises several hundred FETs and further test devices. The gate lengths as designed vary from 50 nm to 5 &micro;m.<br />(b) False-colored scanning electron microscopy image of an FET with 60 nm gate length and a source-drain distance of 600 nm. The 2D electron liquid forms a rectangular region connecting the source and drain electrodes and is surrounded by insulating amorphous LaAlO<sub>3</sub>.</div>

Figure 1

(a) Photograph of a 10 x 10 mm2 sized sample patterned by electron-beam lithography. It comprises several hundred FETs and further test devices. The gate lengths as designed vary from 50 nm to 5 µm.
(b) False-colored scanning electron microscopy image of an FET with 60 nm gate length and a source-drain distance of 600 nm. The 2D electron liquid forms a rectangular region connecting the source and drain electrodes and is surrounded by insulating amorphous LaAlO3.
<div style="text-align: left;"><strong>Figure 2</strong></div>
<div style="text-align: left;">Drain-source transport characteristics of FETs representing three gate length regimes:<br />(a) long channel lengths (<em>L</em><sub>G </sub>= 5 &micro;m), <br />(b) intermediate channel lengths (<em>L</em><sub>G </sub>= 500 nm) with arising short-channel effects and <br />(c) short-channel effect dominated length scales (<em>L</em><sub>G </sub>= 60 nm). <br />The data were taken at room-temperature.</div>
Figure 2
Drain-source transport characteristics of FETs representing three gate length regimes:
(a) long channel lengths (LG = 5 µm),
(b) intermediate channel lengths (LG = 500 nm) with arising short-channel effects and
(c) short-channel effect dominated length scales (LG = 60 nm).
The data were taken at room-temperature.
 
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