Application

The main features of a Schottky-barrier diode are high-frequency capability and low forward-voltage drop. These features plus the ease of fabrication make the device useful in a wide range of applications.

1. As a general purpose rectifier, it can be used in many circuit applications

2. Due to its high-frequency capability, among all rectifiers the Schottky barrier is the most widely used diode as microwave mixer and detector.

3. Due to its low loss (low voltage drop) in forward bias, it is used quite extensively in power electronics. In particular, it is used in low-voltage, high-current power supplies.

4. Due to the non-linear I-V characteristics, it can be used as a varistor

5. It can be used as a varactor based on the variation of depletion-layer capacitance under reverse bias

6. It is a fundamental building block for many other devices such as the solar cell, photodetector, metal-base transistor, MESFET, etc.

7. A special form of Schottky junction is the ohmic contact which is required to connect every semiconductor device to other devices or to the external environment.

8. In a clamped bipolar transistor, a Schottky diode is connected between the base and the collector. In the saturation regime of the transistor operation, the base-collector junction is under forward bias. When a Schottky diode is connected in parallel, most of the current passes through the Schottky device, and minority-carrier storage is eliminated in the base-collector p-n junction. As a result the turn-off time of the bipolar transistor is greatly reduced. It is also used as a clamping diode in integrated injection logic circuits and transistor-transistor logic circuits.

9. Due to the low temperature processing, a Schottky barrier is used as a tool for characterization of the semiconductor material, especially on surface properties.

Related devices Mott Barrier

A Mott barrier has a metal contact on a lightly doped surface layer on a more heavily doped substrate. The lightly doped layer is fully depleted, and the space charge is negligible so that the electric field is constant. The capacitance of the device is small and independent of bias. The current, in this case, is diffusion limited rather than thermionic emission limited.

Metal-Insulator-Semiconductor Tunnel Diode

In the metal-insulator-semiconductor (MIS) structure, a thin interfacial layer such as an oxide is intentionally introduced before metal deposition. The interfacial layer thickness lies in the range of 1-5 nm. The interfacial layer reduces the majority-carrier current without affecting the minority-carrier current, and this raises the minority injection efficiency. This structure is used in other devices such as the solar cell, MISS switch, and surface oxide transistor.

Chapter 4 planar-doped-barrier diode

The planar-doped-barrier (PDB) diode is often called the cS-doped-barrier diode or triangular-barrier diode, due to the shape of the potential barrier. It belongs to a class of bulk-barrier diodes which are different from the most common majority-carrier device, the Schottky-barrier diode whose barrier is formed at the semiconductor surface. The development that led to this device started from the idea of enhancing the Schottky-barrier height by a thin, depleted region of high concentration of the opposite type at the surface, proposed by Shannon in 1974. Shannon, later in 1979, developed a new majority-carrier device called a camel diode in which the metal-semiconductor barrier was eliminated and the barrier was created by an n++-p+-n structure. The planar-doped barrier was first reported by Malik et al. in 1980. The structure differs from the camel diode by having layers of intrinsic regions inserted between the oppositely doped layers, i.e., n+-i-p+-i-n structure.

A typical planar-doped-barrier diode is in GaAs. Because the middle p+-layer has to be fully depleted, it is very thin and it lies in the range of 2-10 nm. Such a thin, heavily doped layer can only be controlled by MBE or MOCVD growth. Besides, thermal cycles during subsequent processing have to be constrained to avoid excessive diffusion. The doping level is typically in the 1018 cm-3 range. The intrinsic regions range from tens of nm to several hundred nm, and have concentrations in the 1014 cm 3 range. The mesa structure can be obtained by etch-back of the planar epitaxial layers.