We present designs and measurements of integrated high resistivity (HR) Si PhC waveguide Bragg reflectors with 100 GHz band gap close to 0.6THz, respectively suspended in air or supported by a teflon tube. Resonant defect modes both in the air and dielectric Bloch bands of the PhC with large Q factors (up to 18000) and high transmittance (up to 72%) are measured and reported by engineering the periodicity of the PhC mirrors.