

MIIM Diode

The metal-insulator-insulator-metal (MIIM) diode is a quantum tunneling device, not based on semiconductors. See “MIIM diode section” in Figure 3471. The insulator layers must be thin compared to the de Broglie electron wavelength, for quantum tunneling to be possible. For diode action, there must be a prefered tunneling direction, resulting in a sharp bend in the diode forward characteristic curve. The MIIM diode has a sharper forward curve than the metal insulator metal (MIM) diode, not considered here.

Fig. 3471: Metal insulator insulator metal (MIIM) diode: Cross section of diode. Energy levels for no bias, forward bias, and reverse bias. After .

The energy levels of M1 and M2 are equal in “no bias”. However, (thermal) electrons cannot flow due to the high I1 and I2 barriers. Electrons in metal M2 have a higher energy level in “reverse bias”, but still cannot overcome the isulator barrier. As “forward bias” is increased, a quantum well, an area where electrons may exist, is formed between the insulators. Electrons may pass through insulator I1 if M1 is bised at the same energy level as the quantum well. A simple explanation is that the distance through the insulators is shorter. A longer explanation is that as bias increases, the probability of the electron wave everlapping from M1 to the quantum well increases. For a more detailed explanation see Phiar Corp.

MIIM devices operate at higher frequencies (3.7 THz) than microwave transistors. The addition of a third electrode to a MIIM diode produces a transistor.

Last Update: 2010-11-19