Disclosed is a deep red phosphor (600 nm to 670 nm) of Mn activity having a chemical formula of (k-x)MgOxAF2GeO2:yMn4+ where k is a real number between 2.8 and 5.0, x is a real number between 0.1 and 0.7, y is a real number between 0.005 and 0.015, and A is Ca, Sr, Ba, Zn, or a mixture thereof, or a mixture of Mg and at least one of Ca, Sr, Ba and Zn. The deep red phosphor has a high excitation efficiency and thus can be applied to light emitting diode (LED) packages, which uses an ultraviolet (UV) light source or a blue light source as an excitation light source. The deep red phosphor is applied to a phosphor layer of a phosphor lamp such as a cold cathode fluorescence lamp (CCFL) and a flat fluorescent lamp (FFL).