Cramer: Up 560%, hot momentum stock?
Because these stocks have all generated significant gains already, Jim Cramer decided to take a deeper dive into all three companies to see if the momentum could endure.

GT Advanced Technologies

"GT Advanced Technologies has more than doubled over the last six months and has rallied 560% in the last year," Cramer noted, with gains largely predicated on two catalysts.

First, "GTAT makes the equipment used to produce solar and sapphire LED products, and the sapphire LED business has really been heating up lately," Cramer explained.



Then, "The second leg of the rally came in November, when investors learned that the company had gone into business with Apple ." Investors bought the stock on speculation that Apple might switch from Corning-made glass for its iPhone touchscreens to more durable sapphire products made by GTAT.

Although that kind of announcement would likely drive a further advance, "We can't be sure that Apple's going to make this move," Cramer said.

Therefore, Cramer sees this stock as a spec play only.



"If you like this story, I say wait for the next market-wide sell off; then you have my permission to buy GTAT, but only for speculation."



----------------------------------------------------------

Read more from Mad Money with Jim Cramer

Candy fix could drive profits

Boeing flying into headwinds?

Where does Cramer see opportunity?

----------------------------------------------------------



SunEdison



In the past year, shares of SunEdison have gained a whopping 350%.

"Until last June, this company was known as MEMC and traded under the symbol WFR," Cramer said. "Some of this move is because the company has grown from a maker of silicon wafers to a full-service solar energy provider with a growing pipeline of projects."

"Also, SunEdison is taking aggressive action to bring out value, mainly by planning to spin-off a minority interest in the company's semiconductor business," Cramer said.

This is exactly the kind of split-up that Cramer talks about so often on "Mad Money."



"I think SunEdison's solar side will get a much higher valuation without the semiconductor division weighing it down," he said.



And SunEdison is also generating shareholder value in other ways. "It's creating a YieldCo vehicle that will own the solar power projects the core business builds and then use the cash to reward investors with a sizable dividend."

How would Cramer play it?



"I'd wait for the SunEdison YieldCo IPO and then try to get a piece of it. That's where the opportunity is with this one."



Incyte

"Incyte develops drugs that treat blood disorders, cancer, and inflammation," Cramer said. Shares have rallied over 150% in a year.



"The stock has surged because which was approved back in November of 2011 has been selling very well. Also, the company has been testing the drug for other ailments. It could give sales a big boost down the road.



"On top of that, Incyte has a strong pipeline including a pancreatic cancer drug that's just starting phase 3 trials and drugs for non-small cell lung cancer, colon cancer and breast cancer that are now in phase 2 trials."

In other words, this drug maker has a very deep bench.

"So, even after the stock's enormous run, I think there's a compelling case that it could go substantially higher based on sales of Jakafi and the power of its pipeline. But, like GTAT, Incyte is only for speculation," said Cramer.