Apple Inc. is developing new iPhone designs including bigger screens with curved glass and enhanced sensors that can detect different levels of pressure, said a person familiar with the plans.

Two models planned for release in the second half of next year would feature larger displays with glass that curves downward at the edges, said the person, declining to be identified because the details aren’t public. Sensors that can distinguish heavy or light touches on the screen may be incorporated into subsequent models, the person said.

With screens of 4.7 inches and 5.5 inches, the two new models would be Apple’s largest iPhones, the person said, and would approach in size the 5.7-inch Galaxy Note 3 that Samsung Electronics Co. debuted in September. The South Korean maker last month released its curved-screen Galaxy Round, the latest phone in an array of sizes and price points that’s helping keep Samsung ahead of Apple in global market share.

The new Apple handsets are still in development and plans haven’t been completed, the person said, adding that the company probably would release them in the third quarter of next year.

Natalie Kerris, a spokeswoman for Cupertino, California-based Apple, declined to comment.

Apple broke with past practice in September when it unveiled two versions of the iPhone at the same time, the iPhone 5S with more advanced features and the iPhone 5C at lower prices, as part of a strategy to appeal to broader markets.

Demand for the iPhone 5S is much higher, and iPhone 5C production has been reduced, the person said.

Revenue growth for the current quarter, Apple’s traditional holiday sales period, may be the slowest since 2008, according to data compiled by Bloomberg based on the company’s financial forecast published last month. Samsung said last month it expects this quarter’s shipment growth rate from the prior quarter to fall to a “low single digit” percentage from the “mid-10 percent range” the prior period.

Testing continues on the pressure-sensitive technology, which is unlikely to be ready for the next iPhone release and is instead planned for a later model, the person said.

Apple’s testing and development of new materials follows its history of working with suppliers to produce new technologies that can enhance device functions. (Bloomberg)