An IGZO display is a not a type of a display panel. To be more specific, an IGZO display is any display panel that uses a backplane thin-film transistor or TFT made of indium gallium zinc oxide or IGZO semiconductor material. Hence, IGZO display technology is compatible with different types of display panels such as twisted nematic or TN LCD, in-plane switching or IPS LCD, and organic light emitting diode or OLED display. To understand further what an IGZO display is, it is important to understand its properties or characteristics and thereby, it benefits or advantages, as well as its limitations and disadvantages.
Benefits: The Advantages of IGZO display
1. Natural Transparency
Note that more light passes through an IGZO-based TFT than silicon-based TFTs such as amorphous silicon or aSi-TF because it is naturally transparent and more compact. Nonetheless, the primary advantage of an IGZO display is its natural transparency.
This transparency translates to energy efficiency. To be more specific, compared to an LCD equipped with an aSi-TFT, an LCD based on an IGZO TFT uses less power due to the reduced need for backlighting intensity. In the case of an OLED, an IGZO TFT reduces the brightness output of individual organic diode. Display panels based on arguably consumes less power than an aSi display while still producing brighter images.
2. Better Electron Mobility
An IGZO semiconductor has 30 to 50 times more electron mobility than amorphous silicon, thus allowing a smaller physical footprint without compromising conductivity. This higher electron mobility corresponds to more specific benefits.
For instance, note that the size of transistors affects the size of the pixel. Due to a higher electron mobility, another advantages of IGZO display when compared to an aSi display is higher pixel density within a smaller display real estate. Earlier IGZO display prototypes had crammed 498 pixels per inch within a six-inch footprint.
It is also worth mentioning that backlighting is obstructed in high pixel density LCD based on aSi-TFT. To compensate, these aSi-based displays consume more power for a more intense backlighting. Power consumption requirement increases with an increase in thepixel density of an aSi-TFT LCD. This is not a problem in IGZO-based TFT LCDs.
3. Low Current Leakage
IGZO has electron mobility that is nearly as high as low-temperature polysilicon or LTPS. However, LTPS has a higher current leakage that results in high power consumption. On the other hand, although aSi has lower current leakage, remember that it also has lower electron mobility than both IGZO and LTPS
The low current leakage and high electron mobility of IGZO give it a more advantageous current flow than aSi and LTPS. This advantage means that the transistors in an IGZO display do not have to be refreshed continuously while displaying a still image because it can retain the active state of its pixels longer due to its advantageous current flow.
On the other hand, displays based on aSi or LTPS need to overwrite still image data through a continuous refresh. Hence, when compared to an IGZO display, an aSi-TFT or LTPS-TFT display consumes 80 to 90 percent more power, particularly when displaying still images such as photographs or documents.
4. Less Noise Influence
Another benefit of IGZO TFT and thus, another advantage of IGZO display is less noise influence. This characteristic is based on the fact that an IGZO is an intermittent type of semiconductor.
To understand further, note that the drive in an IGZO display does not need to be continuous. This allows touch input to be more sensitive or responsive. Although noise is a consequence of touch-sensitive displays, the noise generated by touching an IGZO display is very brief, thereby resulting in a more accurate detection of even the faintest signal.
An IGZO display with a higher degree of touch sensitivity can pick up thinner and finer lines than non-IGZO displays, notably silicon-based TFT displays. Writing on an IGZO display has a closer feel as writing on a paper, thus mimicking natural handwriting input.
Limitations: Disadvantages of IGZO Sisplay
1. Physical and Chemical Characteristics
Note that IGZO is a metal oxide. The high reactivity of oxygen increases susceptibility to very low voltage sensitivity, thus resulting in operation disruption and possible internal failures.
Another disadvantage is lower uniformity of electron mobility when compared to aSi and LTPS that may result in differences in product quality across similar products or batch of units. The same low uniformity of electron mobility may result in operation disruptions or inconsistencies of an individual IGZO-based product.
2. Manufacturing Challenges
IGZO is made from rare-earth metals indium and gallium. The rarity of these metal introduces risks in costs and procurement that could affect mass production and subsequently, expansive applications and standardization in consumer electronic devices due to supply shortages.
Other manufacturing issues collectively represent another disadvantage of IGZO display. To be specific, the current obstacle to mass-producing IGZO is synthesis. The most common used synthesis method in the industry, the Pulsed Laser Deposition or PLD, requires expensive equipment and a considerable amount of time for each output to adapt to environmental conditions. A possible alternative to PLD is combustion synthesis, but its feasibility and practicality needs more research.
3. Negligible Response Time
Remember that one of the advantages of IGZO display is a better response time than aSi-TFT and other silicone-based TFT displays. However, transmissive display technologies such as TN LCD and IPS LCD inherently have slow response times when compared to emissive display technologies, thus rendering this advantage almost negligible. An OLED display based on IGZO TFT can still take advantage of this faster response time.
Takeaway: The Advantages and Disadvantages of IGZO Display
The advantages of IGZO display revolve around its physical properties that enable it to operate under lesser power requirements than its silicone-based counterparts while featuring higher density display regardless of size. These advantages benefit consumer electronic devices such as smartphones and portable computers.
It is also important to reiterate the fact that IGZO is not a type of display panel but rather a type of display technology or manufacturing configuration. This configuration applies to different types of display panels such as TN LCD and TN IPS, as well as OLED or AMOLED displays.
There is also no considerable difference between an LCD or OLED based on aSi-TFT and an LCD or OLED based on IGZO, specifically when it comes to image quality and color reproduction accuracy. However, as discussed above, IGZO-based display panels have considerable advantages such as substantial power saving and smaller physical footprint without compromising pixel density and brightness.
A hybrid between IGZO and LTPS is possible. Apple Inc. demonstrated in its Apple Watch devices that it is possible to combine silicon-based and oxide-based materials with the so-called low-temperature polycrystalline oxide or LTPO display.
