Understanding Ohmic Junctions with Aluminium and Semiconductors

In summary, the conversation discusses the use of aluminum (Al) as a contact metal for both n-type and p-type silicon. This is possible because Al has a high work function that allows it to form an Ohmic junction with both types of semiconductors. Al reacts with oxygen to form Al2O3, consuming the native oxide and facilitating contact formation. However, silicides are now more commonly used due to their improved resistance to diffusion during high-temperature processing.
  • #1
Excom
61
0
Hallo

Is there someone that can explain why Al can be used to form Ohmic contats to both p- and n-type Si?

When looking at a Ohmic junction between a metal and a semiconductor, it is formed when the work functions are as follows: [tex]\Phi_m[/tex]>[tex]\Phi_p[/tex] and [tex]\Phi_m[/tex]<[tex]\Phi_n[/tex]. How can Al fulfil both or is there something that I am not aware of?
 
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  • #2
Does this help:
Aluminum is another important contact metal for silicon which can be used with either the n-type or p-type semiconductor. As with other reactive metals, Al contributes to contact formation by consuming the oxygen in the native oxide. Silicides have largely replaced Al in part because the more refractory materials are less prone to diffuse into unintended areas especially during subsequent high-temperature processing.
Wikipedia: http://en.wikipedia.org/wiki/Ohmic_contact#Technologically_important_kinds_of_contacts
 
  • #3
No it does not help.

I do understand that Al can react with oxygen to form Al2O3 and thereby consum the native oxide. However, this do not explain why Al can make ohmic contact to n- and p-type silicon.
 

1. What is an ohmic junction?

An ohmic junction is a type of electronic junction where the current-voltage relationship follows Ohm's law, meaning that the current through the junction is directly proportional to the voltage applied.

2. How does aluminium affect ohmic junctions with semiconductors?

Aluminium is commonly used as a contact material in ohmic junctions with semiconductors due to its low resistivity and good adhesion to the semiconductor material. It also forms a Schottky barrier at the interface, which helps to reduce the contact resistance.

3. What are the main factors that affect the performance of ohmic junctions?

The main factors that affect the performance of ohmic junctions include the contact material, interface properties, and the characteristics of the semiconductor material, such as doping concentration and type.

4. Can ohmic junctions be used in both forward and reverse bias?

Yes, ohmic junctions can be used in both forward and reverse bias. In forward bias, the voltage applied across the junction allows for the flow of current, while in reverse bias, the junction acts as a diode, allowing for only a small amount of leakage current to pass through.

5. What applications utilize ohmic junctions with aluminium and semiconductors?

Ohmic junctions with aluminium and semiconductors are commonly used in electronic devices such as transistors, diodes, and integrated circuits. They are also used in solar cells, where the junction between the semiconductor and metal contact allows for the conversion of light energy into electrical energy.

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