Method of increasing efficiency of thermotunnel devices

A method for cooling comprising the steps:

• (a) placing a collector electrode a distance d0 from an emitter electrode;
• (b) placing an insulator layer a distance d1 from the emitter electrode, the insulator layer comprising silicon nitride or aluminum nitride and having a thickness of d0-d1;
• and
• (c) contacting the insulator layer and the collector layer;
• (d) applying a bias voltage Vbias to said emitter electrode thereby creating a field E1 in said insulator and a field E2 in a region between said insulator layer and said emitter;
• wherein a barrier for tunneling of high energy electrons is thinner than in the absence of said insulator layer but a barrier for tunneling of low energy electrons is approximately the same as in the absence of said insulator whereby an energy spectrum of the tunneling electrons will shift in the direction of higher energies, thereby enhancing a Coefficient of Performance for cooling.