Browsing by Author "Cherng, YT"

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A new CMOS readout circuit for uncooled bolometric infrared focal plane arrays
(2000)
Yu, TH
;
Wu, CY
;
Chin, YC
;
Chen, PY
;
Chi, FW
By incorporating the basic Constant Current (CC) configuration with the buffered direct injection (BDI) structure, a new readout circuit called the constant current buffered direct injection (CCBDI) is proposed for the uncooled bolometer detector FPAs. Due to the use of BDI structure, the offset is decreased and the linearity range is increase. Thus linearity, dynamic range, and uniformity are improved. An experimental chip of 64x64 CCBDI FPA readout circuit has be designed and fabricated by using 0.5 mu m double-poly double-metal n-well CMOS technology with the cell size of 50x50 mu m(2). The measured linearity is 94.36% whereas the measured uniformity is 81.3%. Both measurement and simulation results have verified the advantageous features of the proposed CCBDI readout circuit. It is believed that the new CCBDI structure has a great potential in the applications of large uncooled bolometer FPAs.
Formation of self-organized GaN dots on Al0.11Ga0.89N by alternating supply of source precursors
(2004-06-15)
Ke, WC
;
Huang, HY
;
Ku, CS
;
Yen, KH
;
Lee, L
The self-organized GaN dot structure is successfully grown on a slightly lattice-mismatched Al0.11Ga0.89N epilayer using flow-rate modulation epitaxy (FME) growth technique. From the variation of dot density with growth temperature, we can observe that the GaN dot growth is controlled predominately by the surface diffusion of Ga adatoms at substrate temperatures below 915degreesC and by re-evaporation at higher temperatures. Because of the special alternating gas supply feature in FME, during the Ga source step, it is the Ga metal that is deposited on the underlying Al0.11Ga0.89N layer. This is because of the large lattice mismatch of 41.8% between the Ga metal (4.51 Angstrom) and Al0.11Ga0.89N (3.18 Angstrom). We consider that the GaN dot growth in our study is mainly through the Volmer-Weber growth mode, not the commonly used Stranski-Krastanow growth mode.
High-performance CMOS buffered gate modulation input (BGMI) readout circuits for IR FPA
(1998-08-01)
Hsieh, CC
;
Wu, CY
;
Sun, TP
;
Jih, FW
;
Cherng, YT
A new CMOS current readout structure for the infrared (IR) focal-plane-array (FPA), called the buffered gate modulation input (BGMI) circuit, is proposed in this paper. Using the technique of unbalanced current mirror, the new BGMI circuit can achieve high charge sensitivity with adaptive current gain control and good immunity from threshold-voltage variations. Moreover, the readout dynamic range can be significantly increased by using the threshold-voltage-independent current-mode background suppression technique. To further improve the readout performance, switch current integration techniques, shared-buffer biasing technique, and dynamic charging output stage with the correlated double sampling circuit are also incorporated into the BGMI circuit, An experimental 128 x 128 BGMI readout chip has been designed and fabricated in 0.8 mu m double-poly-double-metal (DPDM) n-well CMOS technology, The measurement results of the fabricated readout chip under 77K and 5 V supply voltage have successfully verified both readout function and performance improvement. The fabricated chip has the maximum charge capacity of 9.5 x 10(7) electrons, the transimpedance of 2.5 x 10(9) Omega at 10 nA background current, and the active power dissipation of 40 mW, The uniformity of background suppression currents can be as high as 99%. Thus, high injection efficiency, high charge sensitivity, large dynamic range, large storage capacity, and low noise can be achieved in the BGMI circuit with the pixel size of 50 x 50 mu m(2), These advantageous characteristics make the BGMI circuit suitable for various IR FPA readout applications with a wide range of background currents.