HIGH ELECTRON MOBILITY TRANSISTORS Abstract HEMT is a
HIGH ELECTRON MOBILITY TRANSISTORS Abstract: HEMT is a field effect transistor incorporating a junction between two materials with different band gaps as the channel. We will discuss different types of HEMTs and their Applications. Presented by: Sujana Korrapati, Sai Divya Anne Date: 04/28/2014
OUTLINE Introduction Ga. N HEMT structure and operation principles Design rules for Al. Ga. N/Ga. N HEMT In. P HEMT Comparison of Ga. N HEMT with Ga. As HEMT Applications in Technology Summary
INTRODUCTION Transistors are used in electronic devices e. g. switch, amplifiers, oscillators To satisfy the growing demands of Ø High Power Ø High Speed Ø High Efficiency communications Conventional HEMTs use a Al. Ga. As/Ga. As Al. Ga. N/Ga. N
BASIC GAN HEMT STRUCTURE Source: http: //www. eetimes. com/document. asp? doc_id=1272514
GALLIUM NITRATE High electron density(Polarization effects) Adequate for high power amplifiers High Breakdown voltage Large heat capacity Necessary to growth in a wafer of another material Ø Molecular Beam Epitaxy Ø Metal Organic Vapor Beam Epitaxy
SUBSTRATE MATERIAL Sapphire Ø Most used material, cheap, good quality commercial wafers. Ø Poor thermal conductivity. Silicon Carbide Ø Low lattice mismatch. Ø High thermal capacity. Silicon Ø Most common semiconductor. Ø Acceptable thermal conductivity.
OPERATION PRINCIPLES (POLARIZATION) Al. Ga. N/Ga. N HEMTs transistor don’t need doping to obtain a high electron density. Spontaneous polarization. + Piezoelectronic polarization. = 1013 (cm 2/Vs) carrier concentration
ENEGRY BAND DIAGRAM OF GAN/ALGAN HEMT • HEMTs utilize heterojunction between two semiconducting materials to confine electrons to a triangular quantum well. • Conduction band edge EC and Fermi level EF determine the electron density in the 2 DEG Source: http: //research. pbsci. ucsc. edu/chemistry/li/re search. html
HETEROJUNCTION Heterojunction: 2 layers • Highly doped layer with grand gap • Non-doped layer with small gap
DESIGN RULES FOR GAN/ALGAN HEMTS: MATERIALS PERSPECTIVE Thickness of the Barrier Layer Al composition of the barrier layer Nucleation and Buffer layer Substrate for epitaxial growth
DESIGN RULES FOR GAN/ALGAN HEMTS: FABRICATION PERSPECTIVE Gate footprint, cross-sectional area and width controls the frequency response Gate drain spacing as well as gate footprint determines the breakdown voltage Geometry of the device also plays a role
DC CHARACTERISTICS G OFA N/ALGAN HEMTS
INP HEMT Source: http: //www. mwe. ethz. ch/en/about-mwe-group/research/vision-and-aim/highelectron-mobility-transistors-hemt. html
ADVANTAGES OF INP BASED HFETS Lower noise Higher cutoff frequency Higher gain Operating voltage below 3 V
COMPARISON OF GAN HEMT WITH GAAS HEMT ΦB Al. Ga N Ga. N d +ve σcomp σsurf Ec ∆Ec EF σB Al. Ga. A s donor layer Ga. As buffer 2 DEG Al. Ga. N/Ga. N HEMT Al. Ga. As spacer Al. Ga. As/Ga. As HEMT
HEMT APPLICATIONS A Monolithic HEMT Passive Switch for Phased- Array Applications High Power and High Efficiency Ga. N-HEMT for Microwave Communication Applications Highly efficient high power In. P HEMT amplifiers for high frequency applications Highly Uniform In. Al. As–In. Ga. As HEMT Technology for High-Speed Optical Communication System ICs
A MONOLITHIC HEMT PASSIVE SWITCH FOR PHASED- ARRAY APPLICATIONS A 0. 2 x 200 , um 2 HEMT device is used as a series passive FET switch
HIGH POWER AND HIGH EFFICIENCY GAN-HEMT FOR MICROWAVE COMMUNICATION APPLICATIONS In the typical mobile communication band of more than 2 GHz, the RF signal loss through the Cds and Rs becomes significant. Thus, the minimization of Cds is effective in the high efficiency amplification.
INALAS–INGAAS HEMT TECHNOLOGY FOR HIGH-SPEED OPTICAL COMMUNICATION SYSTEM ICS Uniformity of the transistors is required to fabricate highspeed ICs with more than 1000 transistors were fabricated using Y-shaped gate technology and operated at 40 Gb/s
SUMMARY & CONCLUSIONS HEMT transistor are widely used in electronic application Al. Ga. N/Ga. N structure looks promising Al. Ga. N/Ga. N HEMT grown on Si substrate not only reduces the production cost but also prepares for the possible combination of Ga. N devices and Si technology
REFERENCES http: //ieeexplore. ieee. org/stamp. jsp? tp=&arn umber=536950 http: //ieeexplore. ieee. org/stamp. jsp? tp=&arn umber=5877127 http: //ieeexplore. ieee. org/stamp. jsp? tp=&arn umber=1219481 “Characterization of advanced Al. Ga. N HEMT structures” Anders Lundskog. http: //ieeexplore. ieee. org/stamp. jsp? tp=&arn umber=877122
FIVE KEY POINTS ABOUT HEMT 3 contacts: Source and drain ohmic contacts. Gate Schottky barrier Conventional HEMTs use a Al. Ga. As/Ga. As Al. Ga. N/Ga. N High electron density (Polarization effects) The HEMT-HBT monolithic microwave integrated circuit (MMIC) is fabricated using selective molecular beam epitaxy (MBE) In. Al. As-In. Ga. As HEMT grown on In. P substrate promises excellent gain and noise performance for amplifier applications
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