dc.description.abstract | AlGaN/GaN HEMTs have been widely used in RF power amplifiers, especially in base station power transmitters, because GaN-based wide energy gap materials have high electron mobility and high breakdown electric field characteristics. However, the dispersion of current generated in the defects of GaN HEMTs is an important issue.In this paper, different defects were added to the AlGaN/GaN HEMTs analog device for transient simulation analysis, and the AlGaN/GaN HEMTs were subjected to stress in the on state, different static operating points and different substrate temperatures for current transient measurement analysis.
The analog device is an AlGaN/GaN HEMT structure. If acceptor-like traps are added to the SiO2 and AlGaN interface or GaN of the analog device, current may increase or decrease in a continuously on state, but if add donor-like traps, there will be a tendency for the current to increase.
The commercial device AlGaN/GaN HEMTs measured in the paper have a gate length and a gate width of 0.25 μm and 125 μm, respectively, and grow on a 4 inch SiC substrate, passivated by SiN layer and have source-coupled field-plate. The current transient measurement in the on state consists of two parts. One is a current transient measurement of 100 s at a fixed quiescent operating point, and the other is a current transient of 100 s from a quiescent operating point when switching from different operating points to ID = 100 mA/mm and VDS = 28 V. To analyze trap activation energy(Ea), all current transient measurements were performed at 25°C, 40°C, 50°C and 60°C.
The device is subjected to current transient measurement at a fixed quiescent operating point. If the ID of the operating point is 427 mA/mm, there will be a significant trapping effect, and if the working point ID = 33~238 mA/mm, there will be trapping and detrapping effect. However, at 25°C, if the ID of the working point = 33 ~ 345 mA/mm, it will have different transient characteristics with the device at higher temperature(40°C, 50°C, 60°C).
In addition, the devices are switched from different bias states to ID = 100 mA/mm and VDS = 28 V for 100 s current transient measurement. If the ID of the state before switching is greater than 100 mA/mm, there is a significant detrapping effect within 100 s, but if the ID of the state before switching is less than 100 mA/mm, there is a significant trapping effect within 100 s. The device is switched from ID = 100 mA/mm and VDS = 28 V to different bias states for 100 s current transient measurement. If the ID of the switched state is 343 ~ 427 mA/mm or ID = 33 ~ 87 mA/mm, there will be obvious trapping effect within 100 s, if the ID of the switch state is 145 ~ 238 mA/mm within 100 s, there are obvious trapping and detrapping effects.
In this paper, the appropriate defects are also added to the analog device to fit the measured current transient results, which can have a fairly high degree of coincidence. Therefore, the position, energy level and concentration of defects in the device can be estimated by simulation. In all the transient current analysis in this paper, the trap activation energy extracted is somewhat negative, and some values are too small. It can be inferred that the trapping and detrapping effects in this paper, which is not related to temperature, but may be tunneling. Current transient measurements at all static operating points and continuously open states of different devices substrate temperatures show complex trapping and detrapping effects. This study observes that current transient results are closely related to the application of GaN HEMTs in power amplifiers, so further in-depth studies are necessary. | en_US |