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A modified molecular beam epitaxy technique has been used to grow single barrier GaAs/GaN/GaAs heterostructures of both n‐ and p‐type. The temperature‐dependent I(V) measurements show thermally activated conduction over the barrier above about 200 K. A Type I band alignment is indicated by significant offsets in both the conduction and valence bands at the GaAs/GaN heterointerface.

A series of electrical measurements on double barrier resonant tunneling structures is described. It is shown that the bistability effect in the current–voltage characteristics of a double barrier structure can be removed by connecting a suitable capacitor to the external circuit. These measurements cast serious doubt on the recent interpretation of the bistability as an intrinsic space‐charge effect. The temperature dependence of the tunneling current at voltages below threshold is also investigated. An expression for the temperature and voltage dependence of the thermally activated resonant tunneling process is compared with experiment. Finally, the effect of hydrostatic pressure (up to 11 kbar) on I(V) characteristics is studied. It is found that, whereas the pressure has little effect on the low‐temperature I(V) characteristics, the peak/valley ratio at room temperature is significantly reduced. This behavior is attributed to the effect of the higher conduction band minima.