Abstract-This paper presents novel approaches for dual-band bandpass filter design utilizing stepped impedance simplified cascaded quadruplet resonators (SI-SCQRs) with slot coupling. A pair of SISCQRs forms a cross coupled dual-band filtering path to provide high selectivity passband response, and a slot coupling structure provides SI-SCQRs with another filtering path for improving and controlling the performances of the dual-band filter such as insertion loss and bandwidth. Measured insertion losses are 0.26 dB and 1.2 dB, and return losses are better than 16.3 dB and 15.2 dB at the first and second passband frequencies, respectively, with a mid-stopband attenuation around 30 dB.
Valence-subband structures of GaAs-Ga1−xAlxAs quantum wells growth in the [001], [111], and [110] directions are calculated based on the bond-orbital model. The effective mass for the first subband in (111)-oriented quantum wells is found to be substantially smaller than that in (001)-oriented quantum wells for well widths narrower than 70 Å. The subband structures of (110)-oriented quantum wells display large anisotropy, with effective masses along two different in-plane directions ([001] and [11̄0]) differing by almost one order of magnitude. It is also found that the Al composition has a strong effect on the hole effective mass. Implications of our results in device applications are also discussed.
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