Abstract
A hydrogen-terminated diamond (H-diamond) Field effect transistor (FET) with a ferroelectric HfZrOx/Al2O3 stacked gate dielectric was demonstrated for the first time. The HfZrOx(16 nm)/Al2O3(4 nm) gate dielectric was grown by atomic layer deposition (ALD) at 300 °C. The bowknot-like capacitance-voltage hysteresis and the transfer characteristic curves in clockwise hysteresis loop directly illustrated the ferroelectricity of the device. A memory window as wide as 7.3-9.2 V, the maximum on/off ratio of 109 and the subthreshold slope (SS) of about 58 mV/decade was measured for the gate voltage sweeping between 10.0 to −10.0 V in the linear region. A completely normally-off behavior was observed in the saturation region because both threshold voltages ( $\text{V}_{\mathrm {th}}$ ’s) for forward and reverse sweeping transfer characteristic curves are negative at a drain voltage of −15 V. It is ascribed to that the polarization state of the HfZrOx dielectric along the channel changes from uniform in the linear region to strongly nonuniform in the saturation region. These results hint that HfZrOx/Al2O3/H-diamond FETs provide new possibility of diamond normally-off FETs, negative capacitance FETs and non-volatile memory of high density integration.
Highlights
Diamond has many excellent properties from the extremely strong and tight sp3 bonding, such as wide band gap (5.5 eV), the highest electrical breakdown field (10 MV·cm−1), lower dielectric constant (5.7), the high carrier mobility (4500 and 3800 cm2·V−1·s−1 for electrons and holes, respectively), high drift velocity (2.7×107 and 1.1×107 cm·s−1 for electrons and holes, respectively) and the highest thermal conductivity (22 W·cm−1·K−1) in natural materials, which makes it called the ultimate semiconductor [1], [2]
We report the fabrication of an H-diamond Field effect transistor (FET) with a 16 nm hafnium zirconium oxide (HfZrOx) and a 4 nm Al2O3 gate dielectric deposited by atomic layer deposition (ALD) technique
The leakage current density (JGS ) lies below 2.5 ×10−5 A/cm2 in -4 V< VGS < 10 V and increases to 7.1 ×10−5 A/cm2 at VGS = −10 V. This leakage current is at the same level with that of the reported annealing-free HfZrOx (30 nm)/Al2O3 (8 nm) stacked dielectrics [21]. It indicates that the HfZrOx/Al2O3 gate dielectrics deposited on the H-diamond surface is of high quality
Summary
Diamond has many excellent properties from the extremely strong and tight sp bonding, such as wide band gap (5.5 eV), the highest electrical breakdown field (10 MV·cm−1), lower dielectric constant (5.7), the high carrier mobility (4500 and 3800 cm2·V−1·s−1 for electrons and holes, respectively), high drift velocity (2.7×107 and 1.1×107 cm·s−1 for electrons and holes, respectively) and the highest thermal conductivity (22 W·cm−1·K−1) in natural materials, which makes it called the ultimate semiconductor [1], [2]. K. Su et al.: Normally-Off H-diamond FET With Ferroelectric HfZrOx/Al2O3 Gate Dielectrics. The hafnium zirconium oxide (HfZrOx) films have been used to fabricate ferroelectric memories and NCFETs [17]–[20], and those grown by atomic layer deposition (ALD) at 300 ◦ without post-annealing demonstrated strong ferroelectric properties [21]. We expect that the application of annealing-free HfZrOx gate insulator in H-diamond FET could open a new window for H-diamond FeFETs, which would benefit the development of diamond normally-off FETs, NCFETs and non-volatile memory of high density integration. We report the fabrication of an H-diamond FET with a 16 nm HfZrOx and a 4 nm Al2O3 gate dielectric deposited by ALD technique.
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