Australia goalkeeper Mitchell Langerak hopes Bayern Munich's Robert Lewandowski will be fit to face Barcelona in the Champions League semi-final after the striker suffered suspected concussion during a goal-mouth collision.

The Socceroos' shot-stopper was Dortmund's hero in Tuesday's German Cup semi-final as hosts Bayern lost a penalty shootout after the game finished 1-1 after extra-time.

The 26-year-old Langerak saved Mario Goetze's third spot-kick as Bayern missed all four of their penalties to lose the shootout 2-0 and end their dream of a domestic double after securing the Bundesliga title at the weekend.

Lewandowski, Bayern's top scorer with 22 goals, finished the match as a dazed figure following a collision with Langerak late in extra time.

The former Dortmund striker was taken to hospital and is doubtful for next Wednesday's Champions League semi-final, first-leg, at Barcelona.

"I hope Robert is OK, he's a good friend of mine and it was an accident," said Langerak, who is Australia's reserve goalkeeper behind Matt Ryan.

Langerak is set to feature in the final at Berlin's Olympic Stadium on May 30 against either Wolfsburg or minnows Arminia Bielefeld who meet in Wednesday's other semi-final.

"I have never experienced a night like this before, it's hard to find the words," said the former Melbourne Victory goalkeeper who joined Dortmund in 2010.

Langerak was booked for time-wasting just before Germany goalkeeper Manuel Neuer hit the crossbar with Bayern's fourth penalty to send Dortmund to the final.

"I wanted to leave the goalmouth open for as long as possible to increase the pressure," he explained.

"Sometimes it works and today was our day.

"The coach spoke to me before the shootout, but I know what to do in that situation. Penalties are my thing."