Study On The Enhanced Double Heterojunction GaN High Electronic Mobility Transistor

GaN-based microelectronic devices have been researched widely in academia and industry owing to their excenlent properties. Enhanced GaN HEMTs have also attracted huge attention due to their broad application prospect in switching and digital circuit field. The back barrier in double heterostructure HEMT can let the device have good confinement and fluorine plasma treatment is a good way to achieve enhanced device. So it is very significant to develop enhanced device in combination of back barrier and fluorine plasma treatment. In this paper, enhanced double heterostructure(DH) HEMT with low damage is investigated by simulation and experiment.1. Three enhanced DH HEMTs(15nm,30 nm,60nm)using fluorine plasma treatment are achieved by simulation. Firstly,the SH and DH devices' DC characteristicare simulated and the simulation result shows that the DH device has lower 2DEG intensity. Secondly, the DC characteristics of DH devices with different GaN channel thickness are also simulated. The simulation result shows that the threshold voltage(Vt) decreases with the GaN channel thickness increasing and the gm increases with the GaN channel thickness increasing. Lastly, three DH devices with different GaN channel thickness treated with low fluorine plasma power are simulated, all of whose Vt were shifted positively to be larger than 0.2. Three enhanced DH HEMTs(14nm,28 nm,60nm) using fluorine plasma treatment are achieved by experiment, all of whose Vt still remain large values after annealing. Three DH devices with different GaN channel thickness(14nm,28 nm,60nm)were treated with fluorine plasma, while the condition is(135W, 180s), and the Vt is 1.1V?0.8V?0.3V before annealing, respectively and the gm is 110 m S/mm ? 146 m S/mm ? 198 m S/mm before annealing, respectively. In order to repair damages and improve devices' characteristic, annealing was used. The Vt is 0.7V?0.4V(14nm,28nm) after annealing, respectively and the gm is 161 m S/mm?198m S/mm after annealing, respectively. In the aspect of Schottky characteristic, the schottky current increases with the GaN channel thickness increasing under the influence of tunneling mechanism.3. The DH devices' characteristic at different temperature from 20? to 270? are studied by experiment. In the aspect of DC characteristic, the DC characteristic remains the same when the temperature rises from 20? to 70?and the Vt starts to shift negativly when the temperature rises from 70? to 270?. In the aspect of Schottky characteristic, different current transport mechanisms play a role in different temperature range. Tunneling mechanism and collision mechanism play a role for the reverse schottky current, resulting the Schottky current increases first and then decreases. Tunneling mechanism and the thermionic emission mechanism play a role for the positive schottky current, also resulting the Schottky current increases first and then decreases. In the aspect of DIBL effect, the DH device with 14 nm GaN channel thickness has good confinement while the DIBL value is 16 m V/V. But the confinement gets worse as temperature increases. The DH device with 28 nm GaN channel thickness has good confinement while the DIBL value is 30 m V/V, and the confinement remains stable as temperature increases.