[ODCAD] A play of Material in Next Century


In next century, what do we expect for the hi tech industry? The
industry from tele-comunication in wire or wire less, to hand held
electronic device. A lot of expectation is there. Well, one important
factor to meet the expectations is the electronic materials. Si based
technology may not meet all of the exepectation such as flxible
display device. Organic material, epecially polymer play important
role. A good article on www.mrs.org/publications/bulletin has a
detailed discussion about the electronic materials and its
application in hi tech.

ODCAD from OD Software Incorporated (ODSI)(http://www.odcad.com/)-the expert and toolkit provider of electronic material, device.

[ODCAD] Organic Semicondutors and Devices

Organic material from small molecule like Alq3 to large molecule like conjugated polymer are semi conductor. They have advantage of low cost, low energy consumption, unique electric and optical properties. This type of material can be used to make Diode, Memory, Transistor, and Display device (OLED) etc.

The reader can visit the electronic device group to get more articles.

ODCAD from OD Software Incorporated (ODSI) http://www.odcad.com/ -the expert, and tool kit provider of electronic material and device

[ODCAD] Mobility Effect :Junction of Organic Semiconductor, Electrode
The charge carrier mobility of organic semiconductor is usually much lower than crystal Si material. This low mobility has impact to the transistor (see "Organic TFT Transistor: Interface and Performance"). Also, it has impact to the electrical behavior of the other device.

For a layered structure device, say a simple three layer DIODE device: bottom electrode, middle semiconductor, top electrode. Assume the bottom junction is ohmic, then the diode is due to the top junction. One popular approximate equation is Schottky junction model. The reversed current J0 measured for the junction is usually 6 order (or higher) less than what the model predicts (see "Reversed Current in Schottky Junction"). What is the reason to cause this?

There are quite few reasons for this. One important effect is due to the slow mobility of the charge carrier. A complete model considering charge injection and charge diffusion is Thermionic Emission-Diffusion model (Sze 2nd Edition). In this model, the mobility effect (drift velocity) is trivial if it is large enough compared with thermal charge carrier velocity. Otherwise, the injected current is proportion to the drift velocity that is the product of mobility and field. Dr. Scott from IBM lab in San Jose, CA) has done a set of experiments and the results have confirmed the mobility effect.


This does tell us that the current can be dependent on the mobility even it is at junction control. For device engineer, he (she) has to design (choose) the material to ensure the current obtained from the device can meet the requirements.


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