PAM-XIAMEN offers GaN on Si HEMT wafer for Power, D-mode. Because of the heterojunction structure of GaN and AlGaN, the GaN HEMT on Si Substrate structure has one important property of high electron mobility. More specific info about the structure, please see below:
1.Structures of GaN on Si HEMT Epi Wafer
1.1 D-MODE GaN on Silicon HEMT Wafer Structure
|Wafer size||2″, 4″, 6″,8″|
|AlGaN/GaN HEMT structure||Refer 1.2|
|Carrier density||>9E12 cm2|
|AFM RMS (nm）of 5x5um2||<0.25nm|
|SiN passivation layer||0~5nm|
|u-GaN cap layer||2nm|
|AlGaN barrier layer||/|
|Substrate material||Silicon substrate|
|Si wafer thickness (μm)||675um(2″), 1000um(4″), 1300um(6″), 1500um(8″)|
1.2 AlGaN/GaN on Si HEMT Structure
2. What is a D Mode GaN HEMT?
The interface between the AlGaN and GaN materials in the GaN on Si HEMT epitaxial wafer forms a layer of high-mobility electrons called “two-dimensional electron gas (2DEG)” due to the crystal polarity, which forms a natural layer between the source and drain of GaN on Si power device. The channel gives the GaN HEMT an inherent normally-on property, that is, a depletion mode (D-type) device.
The normally-on characteristic is the main obstacle to the application of GaN on Si HEMT, because in the power converter when the gate drive outputs zero voltage, the switch must be kept in the normally-off state, and the negative turn-off gate voltage of GaN HEMTs requires higher complexity of the gate drive circuit, and also increases the risk of circuit failure. Therefore, D-type GaN HEMT and silicon-based low-voltage E-type MOSFET are usually packaged together to form a cascode device. The drain-source voltage of the MOSFET determines the gate-source voltage of the HEMT, forming a normally-off device, and its driving circuit can be driven by a traditional silicon-based device.