Gamma ray frequency is higher than microwaves.
Gamma rays have a shorter wavelength than microwaves (see chart) http://www.pion.cz/en/article/electromagnetic-spectrum.
Gamma rays are the highest energy EM radiation and typically have energies greater than 100 keV, frequencies greater than 1019 Hz, and wavelengths less than 10 picometers.
*Source: Boundless. “Gamma Rays.” Boundless Physics Boundless, 08 Aug. 2016. Retrieved 01 Feb. 2017 from https://www.boundless.com/physics/textbooks/boundless-physics-textbook/electromagnetic-waves-23/the-electromagnetic-spectrum-165/gamma-rays-598-11179/*
See also: http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html
for a comparison of all electromagnetic spectrum energy, wavelength and frequencies.