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Resonant tunneling transport was studied in GaAs-AlGaAs single well, double barrier structures. Negative differential resistance at 77 and 300 K was observed in devices grown by metalorganic chemical vapor deposition. The observed peak to valley ratios were 6 to 1 and 1.48 to 1, respectively. The presence of GaAs spacer layers was found to have a distinct effect on the 300 K current versus voltage characteristics. Microwave oscillation at frequencies up to 3.0 GHz was observed at 300 K. A short discussion of the oscillation frequency limits of our structure is presented.

Tunneling magnetoresistive (TMR) readers capable of 150 Gb/in 2 of areal density magnetic recording for hard disk drive were demonstrated with bit-error-rate performance. The head design used is basically a bottom type stack of Ta/PtMn/CoFe/ Ru/CoFe/oxide barrier/CoFe/NiFe/Ta cap with abutted hard bias stabilization. The electrical reader width is about 4 to reach a very high track density and shield-to-shield spacing is about 700 A for high linear density. On-track bit error floor is better than 10 5 at a linear density of 900 KBPI and the recording system noise is dominated by the media. The best areal density achieved (using 4 OTC reference level) is 143 Gb/in 2 using symmetric squeeze and 152 Gb/in 2 using asymmetric squeeze method, respectively. It was found that the TMR head has several decibels more signal-to-noise ratio gain over spin valve readers at 150 Gb/in 2 and beyond. The TMR head is also suitable for perpendicular recording application.Index Terms-Areal density, current-perpendicular-to-plane (CPP) geometry, perpendicular recording, signal-to-noise ratio (SNR), tunneling magnetoresistive (TMR) heads.

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To meet such challenges for the controlling of critical feature dimension at sub-50-100-nm, it has been a general industrial trend to employ shorter wavelength ͑193 nm, for example͒ lithography for better resolution and to use bottom antireflective coating ͑BARC͒ for a reduced standing wave formation and thus, a better critical dimensional control. Matching the optical constants ͑n , k͒ between the BARC, photoresist, and the underlayer to be patterned is critical for the elimination of such standing waves. SiO x N y and SiO x C y are two attractive inorganic BARC candidates in view of their easily adjustable optical constants by varying the deposition parameters and their etching compatibility with standard semiconductor plasma processes. In this article, SiO x N y films were prepared by plasma enhanced chemical vapor deposition approach. These films have been further characterized using x-ray photoelectron spectroscopy for chemical composition depth profile, Fourier transform infrared spectroscopy for local chemical bonding, and ellipsometry for optical constants. It has been demonstrated that the refractive indices of SiO x N y can be tuned from 1.6 to 2, while the absorption constants k can be adjusted from 0.1 to 0.9 by changing the process parameters, such as SiH 4 flow rate, NH 3 flow rate, and SiH 4 /N 2 O ratio. To integrate the SiO x N y BARC film into the storage device manufacturing, the pattern transferring capability of SiO x N y has been discussed. A film stack structure of photoresist/SiO x N y /carbon or SiC hard mask/magnetic device layer has been used to evaluate the performance of the SiO x N y BARC. SiO x N y film was opened via inductively coupled plasma etching with CHF 3 +O 2 chemistry, while carbon and SiC hard masks were opened using He-O 2 and SF 6 -He-O 2 chemistries, respectively. SiF emission line at 388 nm wavelength was used for end point during the SiO x N y etching, while the 778 nm O peak and 685 nm F peak have been used for carbon and SiC end pointing. The profiles of the etched SiO x N y and carbon/SiC were analyzed by cross-section transmission electron microscopy.