Investigation of InGaAsP Heterostructure Field-effect Transistors and Photodiodes

• Main Authors: Yen-Wei Chen, 陳彥瑋
• Other Authors: Wei-Chou Hsu
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/18751726378451419336

博士 === 國立成功大學 === 微電子工程研究所碩博士班 === 92 === In this dissertation, we have successfully fabricated and investigated InP-based InGaAsP heterostructure field-effect transistors (HFET's) and p-i-n photodiodes (PIN-PD's) grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD). The characteristics of InAlAs/InGaAsP HFET's and InGaAsP/InP PIN-PD's are measured and discussed. We describe the properties of the planetary MOCVD reactor. The growth parameters and characteristics of the epi-layers are discussed and analyzed. A series of specialized measurements, including double-crystal x-ray diffraction (DCXRD), photoluminescence (PL), Hall measurement, electrochemical capacitance-voltage (ECV) profile, Lehighton and Surface-scan are used to qualify material characteristics. Improved material uniformities and qualities are demonstrated. Thickness uniformity of the epi-layer within 5%, wavelength uniformity of the quaternary InxGa1-xAsyP1-y layer within 5 nm and lattice mismatch of epi-layer kept within 500 ppm are achieved. Furthermore, the In0.53Ga0.47As layer background concentration lower than 7x1014 cm-3 and the electron mobility higher than 12000 cm-2/v•s are achieved. InAlAs/InxGa1-xAsyP1-y high electron transistors (HEMT's) with various InxGa1-xAsyP1-y channels were demonstrated. Improved linearity characteristics are achieved in the structures utilizing compositionally graded InxGa1-xAs channel and composite InxGa1-xAsyP1-y triple channels due to the improved confinement and transport characteristics. By thinning the InAlAs barrier layer of PCHEMT, enhancement-mode operation is obtained. As the gate bias is sufficiently large, the device exhibits a pronounced N-shaped NDR behavior since hot electrons tunnel from the InGaAs channel layer to the gate electrode. On the other hand, an InAlAs/InGaAs doped channel field-effect transistor (DCFET) was fabricated to improve device linearity, current drivability and breakdown voltage. Experimentally, high transconductance, high current drivability, high linearity, low leakage current and high breakdown voltage are achieved due to the doped InGaAs channel, undoped InAlAs Schottky layer and good carrier confinement. Moreover, a delta-doped InAlAs/InGaAs HEMT with a graded InxGa1-xAs V-shaped channel (DDHEMT) is fabricated. The delta-doping carrier supply layer and graded V-shaped channel are used to enhance two-dimension electron gas (2DEG) density and mobility. Moreover, the improved carrier confinement in the channel is achieved. Experimentally, improved transport performance, including high transconductance, high current drivability, high linearity and high breakdown is achieved. Finally, a series of planar InGaAs(P)/InP PIN-PD's were fabricated and demonstrated. High-quality and uniformity of the epi-layers are obtained. The measured concentrations of In0.53Ga0.47As and In0.66Ga0.34As0.73P0.27 (1.4 PQ) absorption layers are as low as 4.5x1013 and 2.4x1014 cm-3, respectively. Experimentally, the dark current is significantly reduced in the structure utilizing a wider-band-gap material of quaternary InxGa1-xAsyP1-y as a cap layer to reduce the device surface leakage current and dark current. In addition, the wide-band-gap cap layer may also reduce the incident light absorption in the cap layer, thus improving device responsivity. The PIN-PD's with a wide-band-gap InP cap layer in the InxGa1-xAsyP1-y material system can be expected to further improve device performances.