Abstract:
The requirements of communication industry have put a key challenge for
semiconductor industry to develop the devices with high frequency operations. The
terrific carrier transport properties of III–V compound semiconductors, coupled with
100-nm device structures have outstanding high-frequency characteristics, which can
meet the future requirements of communication industry. The high electron mobility
transistors (HEMTs) on Indium Phosphide (InP) substrates have shown important
developments in the last three decades meeting the rising demands for faster devices
specially above 100GHz. High-frequency characteristics of InGaAs/InAlAs HEMTs on InP
substrates, stem from the combination of harmonious size scaling, parasitic reduction,
and an increase of InAs composition in the channel to improve carrier transport
properties.
In this thesis, we designed InAlAs/InGaAs lattice matched Single Gate HEMT (SGHEMT)
and Double Gate HEMT (DGHEMT) structures to target high fT and fmax in THz frequency
range. Silvaco TCAD is used to design and evaluate the performance of these HEMT
structures.
Initially SGHEMT structure having 300nm gate length was designed as a reference HEMT
and design was validated by comparing the results with the published data [21].
SGHEMT was redesigned by decreasing the gate length to 100nm and 50nm. Reduction
of gate length resulted in enhancement of frequency, which was the goal of the thesis
but short channel effects were introduced below 100nm gate length. To overcome these
effects, DGHEMT structure was designed with one gate above the channel and other
below. A novel Double Gate Double Recess HEMT (DGDR HEMT) structure was designed
to improve the overall device performance. It is shown that improvement in frequency
along with suppressing the short channel effects is achieved with optimizing the DGDR
HEMT structure.
