Thermoactivated negative photoconductivity has been observed and investigated in p-GaAs/Al0.5Ga0.5As heterostructures under illumination with the red light in the temperature interval 1.5 – 20 K. Uniaxial compression up to 4.4 kbar was used as an additional parameter changing the energy spectrum of 2D holes. Temperature dependences of the 2D hole concentration and mobility in the thermoactivated photoconductivity state can be described by a model with deep donor like traps in the vicinity of the heterointerface below the Fermi level, if a barrier EB = 6 meV between the ground and excited states is introduced. These traps are supposed to be in the spacer at the distance 7 – 48 nm from the heterointerface.