Schottky Diodes Prepared with Ag, Au, or Pd Contacts on a MgZnO/ZnO Heterostructure

Abstract

We successfully fabricated lateral Schottky diodes with a thin MgZnO layer inserted between the ZnO and Schottky contact metal layers. The MgZnO/ZnO heterostructure was deposited onto a c-sapphire substrate by pulsed laser deposition using Mg0.3Zn0.7O and ZnO targets. Ti/Au was used to achieve ohmic contact with the Mg0.3Zn0.7O thin film layer, whereas Schottky contacts were prepared using silver (Ag), gold (Au), and palladium (Pd). The Ag Schottky diode devices exhibited rectification ratios as high as ∼103 at a bias voltage of ±1 V, with an ideality factor of 2.37 and a work function of 0.73 eV. The possibility of preparing Schottky contacts with a high carrier concentration on the ZnO layer is discussed as a function of the presence or absence of a MgZnO thin layer and in terms of the measured current–voltage properties.

Great Enhancement Effect of 20–40 nm Ag NPs on Solar-Blind UV Response of the Mixed-Phase MgZnO Detector

“…The Ag NPs not only enhances the UV response of the MgZnO detector at deep UV light but also greatly decreases the I dark noise level and increases the signal/noise ratio of the MgZnO detector, which has been reported to be mainly due to the localized Schottky junction at the interface between the Ag NPs and MgZnO thin film. 34 , 36 , 37 The barriers between the Ag NPs and MgZnO thin film are much thicker and the barriers are much higher at higher bias voltages under dark conditions, so the dark current of the MgZnO detector with 100 nm Ag NPs is much smaller than that of the detector without Ag NPs, 38 and the I uv / I dark ratio of the MgZnO detector with 100 nm Ag NPs at a 25 V bias voltage is much higher than that of the bared device.…”

“…To find out if the Ag NPs induces much higher internal gain from hole trapping mechanism, the time response curves of the mixed-phase MgZnO-based detectors without and with 20–40 nm Ag NPs are measured, as shown in Figure 4 e,f. The rise time ( t r ) of the two MgZnO detectors are obtained through fitting of the photo response rise curves by adopting an exponential relation equation as shown in eq 3 , and the decay times ( t d1 , t d2 ) of the two MgZnO detectors are obtained through fitting of the photo response decay curves by adopting a biexponential relation equation, as shown in eq 4 ( 36 ) where y 0 is the steady-state photocurrent, t is the time, y 1 and y 2 are constants, t r is the rise time constant, and τ d1 and τ d2 are the relaxation time constants corresponding to two components (fast and slow). The rise time (t r ) of the bared MgZnO-based UV detector is 20 μs, and the two decay times (t d1 and t d2 ) of the device are 0.6 and 9.8 ms, respectively ( Figure 4 e).…”

“…The I dark of the MgZnO detector with 100 nm Ag NPs increased from 2.22 to 13.5 nA when the bias voltage increased from 5 to 25 V, and the I dark of the detector at different bias voltages is much smaller than that of the bared detector, so the I uv / I dark ratio of the detector reached 74 at a 25 V bias voltage, which is 14.7 times of that of the bared device (Figure d). The Ag NPs not only enhances the UV response of the MgZnO detector at deep UV light but also greatly decreases the I dark noise level and increases the signal/noise ratio of the MgZnO detector, which has been reported to be mainly due to the localized Schottky junction at the interface between the Ag NPs and MgZnO thin film. ,, The barriers between the Ag NPs and MgZnO thin film are much thicker and the barriers are much higher at higher bias voltages under dark conditions, so the dark current of the MgZnO detector with 100 nm Ag NPs is much smaller than that of the detector without Ag NPs, and the I uv / I dark ratio of the MgZnO detector with 100 nm Ag NPs at a 25 V bias voltage is much higher than that of the bared device.…”

Characterization of Ag Schottky Barriers on Be0.02Mg0.26ZnO/ZnO Heterostructures

“…Establishment of high‐quality Schottky contacts is necessary to achieve gate modulation in heterostructure field effect transistors (HFETs). However, only a few studies have been reported on Schottky contacts to MgZnO with, for example, a barrier height of 0.73 eV, an ideality factor of 2.37, and a rectification ratio of only 10 3 . Among various Schottky metals used for ZnO, Ag has been widely adopted because of its potential to create a relatively high Schottky barrier height (1.11 eV on bulk ZnO) with an ideality factor close to unity (1.08) .…”