A double barrier tunnel diode (10) has a quantum well (12), a pair of electron injection layers (16) on either side of the quantum well (12), and a barrier layer (14) between each of the electron injection layers (16) and the quantum well (12), in a strained biaxial epitaxial relationship with the quantum well (12). The material of the quantum well (12) is chosen such that the biaxial strain is sufficient to reduce the energy of heavy holes in the quantum well (12) to less than the energy of the conduction band minimum energy of the electron injection layers (16). Preferably the quantum well (12) is made of gallium antimonide with from about 1 to about 40 atomic percent arsenic alloyed therein, the electron injection layers (16) are made of indium arsenide, and the barrier layers (14) are made of aluminum antimonide.