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Hot electron induced non-saturation current behavior at high electric field in InAlN/GaN heterostructures with ultrathin barrier

View Article: PubMed Central - PubMed

ABSTRACT

The high-field transport characteristics of nearly lattice-matched InAlN/GaN heterostructures with different barrier thickness were investigated. It is found that the current in the InAlN/GaN heterostructures with ultrathin barrier shows unsaturated behaviors (or secondary rising) at high voltage, which is different from that of AlGaN/GaN heterostructures. This phenomenon is more obvious if the barrier thickness is thinner and the channel width is narrower. The experimental results demonstrate that it is the increasing carrier density excited from the more defect states by the hot electrons with larger electron saturation velocity that results in the unsaturated current behaviors in InAlN/GaN heterostructures. Our results pave a way for further optimizing InAlN barrier design and improving the reliability of InAlN/GaN HEMTs.

No MeSH data available.


The schematic H-shaped test structure used for the measurements.
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f1: The schematic H-shaped test structure used for the measurements.

Mentions: Table 1 shows the sample information including barrier thickness, electron mobility (μ) and sheet density (n) measured at room temperature by a Hall Effect measurement system with Van der Pauw method. With the thickness of the InAlN barrier increasing from 4 to 100 nm, the electron sheet density increases from 1.75 × 1013 to 2.60 × 1013 cm−2, and the mobility decreases from 1500 to 790 cm2/Vs. Figure 1 gives the schematic H-shaped test structure. The current-voltage (I-V) curves of the AlGaN/GaN heterostructure shown in the Fig. 2 are the typical characteristics for GaN-based material system17. When the applied voltage changing from low to high values, there appear three regions that show different relationships between current and voltage. At the low electric field region, there is a linear relation where the Ohm’s law is obeyed, and the current linearly relies on the voltage. With further increasing voltage, the relation becomes sublinear, which is due to the fact that the electron energy is gradually enhanced and so that more serious scattering is induced, leading to electron mobility decrease and a sublinear dependence between current and voltage. Finally, when the voltage is above 80 V (about 80 kV/cm for the electric field), the current gradually rises into the saturation region, the saturation velocity (vsat) can be inferred from current density:


Hot electron induced non-saturation current behavior at high electric field in InAlN/GaN heterostructures with ultrathin barrier
The schematic H-shaped test structure used for the measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120260&req=5

f1: The schematic H-shaped test structure used for the measurements.
Mentions: Table 1 shows the sample information including barrier thickness, electron mobility (μ) and sheet density (n) measured at room temperature by a Hall Effect measurement system with Van der Pauw method. With the thickness of the InAlN barrier increasing from 4 to 100 nm, the electron sheet density increases from 1.75 × 1013 to 2.60 × 1013 cm−2, and the mobility decreases from 1500 to 790 cm2/Vs. Figure 1 gives the schematic H-shaped test structure. The current-voltage (I-V) curves of the AlGaN/GaN heterostructure shown in the Fig. 2 are the typical characteristics for GaN-based material system17. When the applied voltage changing from low to high values, there appear three regions that show different relationships between current and voltage. At the low electric field region, there is a linear relation where the Ohm’s law is obeyed, and the current linearly relies on the voltage. With further increasing voltage, the relation becomes sublinear, which is due to the fact that the electron energy is gradually enhanced and so that more serious scattering is induced, leading to electron mobility decrease and a sublinear dependence between current and voltage. Finally, when the voltage is above 80 V (about 80 kV/cm for the electric field), the current gradually rises into the saturation region, the saturation velocity (vsat) can be inferred from current density:

View Article: PubMed Central - PubMed

ABSTRACT

The high-field transport characteristics of nearly lattice-matched InAlN/GaN heterostructures with different barrier thickness were investigated. It is found that the current in the InAlN/GaN heterostructures with ultrathin barrier shows unsaturated behaviors (or secondary rising) at high voltage, which is different from that of AlGaN/GaN heterostructures. This phenomenon is more obvious if the barrier thickness is thinner and the channel width is narrower. The experimental results demonstrate that it is the increasing carrier density excited from the more defect states by the hot electrons with larger electron saturation velocity that results in the unsaturated current behaviors in InAlN/GaN heterostructures. Our results pave a way for further optimizing InAlN barrier design and improving the reliability of InAlN/GaN HEMTs.

No MeSH data available.