One-dimensional thinking led by European researchers

One-dimensional thinking led by European researchers
Europe leads the way in one-dimensional nanoscale semiconductor heterostructure research, according to Professor Lars Samuelson, head of the Nanometer Consortium at Lund University in Sweden. One-dimensional heterostructures could be used to build smaller lasers and high-speed transistors.

Samuelson said: "The European effort is quite a bit ahead of the two US efforts in the field."

Samuelson's Swedish group believes its results are more significant than its US counterparts as they have grown InAs/InP nano-whiskers and measured the abruptness of the heterointerfaces with atomic resolution.

They are also the first group to evaluate the heterostructure energy band diagram properties of a 1-D system. This they believe is a crucial breakthrough for future electronic heterostructure applications designed and created inside nanowires.

The team's method is also different from the spontaneous technique employed by the US group. The Swedish group controls the direction and speed of growth.

"Our technique allows whiskers to be created on pre-defined positions," professor Samuelson said. "We can integrate local whisker-based vertical electronic devices with conventional planar circuit technology.

"The nanowhisker is seeded by a crystalline substrate, resulting in a whisker that grows in a predefined location as well as direction in space."

Obtaining sharp interfaces between the heterobarriers is another area where the European team leads. Professor Samuelson said: "In our technique the growth rate can be kept on the level of one atomic monolayer per second for optimal heterostructure control, while the other techniques typically give very high growth rates, which is obviously extremely difficult to use for tight heterostructure control."

The team claims that the new technique could offer down-scaled heterostructure electronics and photonic devices, such as heterostructure bipolar transistors, double-barrier resonant tunnelling devices and ultra small semiconductor quantum dot lasers.