  A new technique permits high fidelity measurement of the tunneling density of
states (TDOS) of the two-dimensional electron gas. The obtained TDOS contains
no distortions arising from low 2D in-plane conductivity and includes the
contribution from localized tunneling sites. In a perpendicular magnetic field,
a pseudogap develops in the TDOS at the Fermi level. Improved sensitivity
enables resolution of a linear dependence of the TDOS on energy near the Fermi
energy. The slopes of this linear gap are strongly field dependent. The data
are suggestive of a new model of the gap at low energies.
