Dear Nuru,

a homojunction occurs, if only the conductivity-type changes - as an example: from n-type silicon to p-type silicon. A heterojunction almost is present, if only the gap energy changes - as an example from GaAs to GaAl1-xAsx.

In your case, n-type TiO2 and p-type TiO2 , I assume, it is a homojunction. But be carefully - if the doping level with Al is high you could have a new alloy. If doping changes the gap energy, it is a heterojunction.

Yours

R. Mitdank

Dear Nuru,

a homojunction occurs, if only the conductivity-type changes - as an example: from n-type silicon to p-type silicon. A heterojunction almost is present, if only the gap energy changes - as an example from GaAs to GaAl1-xAsx.

In your case, n-type TiO2 and p-type TiO2 , I assume, it is a homojunction. But be carefully - if the doping level with Al is high you could have a new alloy. If doping changes the gap energy, it is a heterojunction.

Yours

R. Mitdank

dear colleague

this question is basical in semiconductor sciences.

junction is the assembling of two semiconductors of different doping (n and p),

when the two semicuctors have the same bandgap : eg: Si(n)/Si(p) it is called HOMOJUNCTION

when the two semicuctors do not have the same bandgap : eg: Si(n)/Ge(p) it is called HETEROJUNCTION

ragards

Semiconductor devices like diodes, Schottky diode, heterojunction, homojunction devices and heterostructures have made remarkable changes in our everyday life.

A homojunction uses the same semiconductor material (of course with different doping) on both sides of the junction, a heterojunction uses two semiconductor materials having different bandgap energies on both sides of the junction.

Like Rüdiger mentioned a heterojunction is between different materials like Ge/GaAs and a homojunction is within the same material like Si with different doping types on either side of the junction. In some cases like Chalcopyrites you get a heterocontact due to a e.g. Cu deficiency at the surface ( ordered vacancy compound ) in CuInSe2. In any case you have a variation of the gap across the junction you can think of a hetero contact.

Dear Nuru,

in addition to these exhaustive answers, in your specific case of n-TiO2 and p-TiO2, you should have to take in account that a heterojunction is possible, in reason of the crystal phase composition of TiO2.

The most common crystal phases for titanium dioxide are Anatase and Rutile, which are characterized by two different band gaps (i.e. 3.2eV and 3.0eV respectively).

This is why a heterojunction is possible too.

In order to have a facile feedback you can characterize your TiO2 samples first through X-ray diffraction for the phase composition and in addition with Diffusive Reflectance Spectroscopy for the band gap estimation (linked you can find an opened topic about the band gap estimation method: https://www.researchgate.net/post/Tauc_Plot_Vs_Kubelka-Munk_plot ).

In a simplest deffinition, a homojunction is a junction between the same materials with the same crystalline structure. A heterojunction is a junction between different materials or between the same materials, but with different crystal structure.

Hetero junction: p-n-junction

Homo junction: p-channel, n-channel

Dear Nurul Islam,

The difference between Homojunction and Heterojunction is shown below:

01. Homojunction:

• Is a semiconductor interface that befalls within layers of alike semiconductor material. These materials have similar band gaps but typically have unusual doping.
• Junctions between differently doped regions of the same semiconductor material are called a homojunction.
• A homojunction is a semiconductor interface that occurs between layers of similar semiconductor material, these materials have equal band gaps but typically have different doping.
• In most practical cases a homojunction occurs at the interface between an n-type (donor doped) and p-type (acceptor doped) semiconductor such as silicon, this is called a p-n junction. This is not a necessary condition as the only requirement is that the same semiconductor (same band gap) is found on both sides of the junction, in contrast to a heterojunction.
• An n-type to n-type junction, for example, would be considered a homojunction even if the doping levels are different.

02. Heterojunction:

• Is an interface that befalls within two layers or regions of different crystalline semiconductors. These semiconducting materials have irregular band gaps.
• Junction between two different types of materials is called a heterojunction.
• A heterojunction is the interface that occurs between two layers or regions of dissimilar crystalline semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction. It is often advantageous to engineer the electronic energy bands in many solid-state device applications, including semiconductor lasers, solar cells and transistors ("heterotransistors") to name a few.
• The combination of multiple heterojunctions together in a device is called a heterostructure, although the two terms are commonly used interchangeably. The requirement that each material be a semiconductor with unequal band gaps is somewhat loose, especially on small length scales, where electronic properties depend on spatial properties.
• A more modern definition of heterojunction is the interface between any two solid-state materials, including crystalline and amorphous structures of metallic, insulating, fast ion conductor and semiconducting materials.

I hope I have answered your question.

With Best Wishes,

Samir G. Pandya

homojunction means the device consist of two or more junctions based on one semiconductor material with difference doping (intrinsic and extrinsic)

heterojunction means the device consist of two or more junctions based on two or more difference semiconductor materials with difference doping (intrinsic and extrinsic)

homojunction- silicon pn junction , here they have same band gap.

heterojunction- Bjt's and Fet's here in that material thy will have different band gap.

Dear Nurul,

TiO2 is an n-type semiconductor, when it is doped with Al. Due to the Al doping TiO2 behaves as a p-n junction. Then the sample is Hetero junction.